In brief: decent 2160p, 250W TDP (OC'ed cards have xxW and over power targets). HDMI 2.0b and Display Port 1.4(ready). Requires one 6-pin and 8-pin PCIe Graphics power connector, but OEM designs may use two 8-pin. Dimensions stated as: a" x b" x c" are from mfgr websites - others are from reviews.

Nvidia reference design @ Techpowerup, Tech Report, Anandtech, Tom's Hardware

Roundups:
hardwareLUXX (German) Corsair Hydro, EVGA SC2 Gaming, Gigabyte Xtreme Edition, KFA2 EXOC, KFA2 HOF, MSI Gaming X, Palit Gamerock PE, Palit Super JS, Zotac Arctic Storm

Reviews with acoustic testing:

Asus GTX 1080 Ti STRIX OC 11GB 11.73-11.97" length, 5.12-5.28" height (~1" above bracket), 2.07" width (2.5 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to 47C; fans on with rise to 55-60C. 70C target temp. 2 HDMI, 2 DP, 1 Dual-link DVI).
Techpowerup
KitGuru
HardwareInfo
hardwareLUXX
Hexus
Guru3D
ComputerBase
Gamers Nexus
Tom's Hardware

Asus ROG Poseidon GTX 1080 Ti Platinum needs a longer name Edition 11GB 11.42" length, xx" height (~x" above bracket), xx" width (2.5 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to xxC; fans on with rise to 60C. Liquid cooling mode - fans are off. xxC target temp. 2 HDMI, 2 DP, 1 Dual-link DVI).
Tom's Hardware
Guru3D

Inno3D iChill GTX 1080 Ti X3 xx" length, xx" height (xx" above bracket), 6-pin and 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to 44C; fans on with rise to 60C. 1 HDMI, 3 DP, 1 Dual-link DVI). 3-slot.
Hexus (pre-production unit)

MSI GTX 1080 Ti Gaming X 11.02-11.5" length, 5.51-5.71" height (xx" above bracket), 2" width (2.5 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to xxC; fans on with rise to 60C. 2 HDMI, 2 DP, 1 Dual-link DVI).
Guru3D
Techpowerup
Gamersnexus
Hexus
Tom's Hardware
KitGuru

MSI GTX 1080 Ti Lightning Z 12.2-12.6" length, 5.12-5.51" height (xx" above bracket), xx" width (2.5 slot), THREE 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to xxC; fans on with rise to 60C. 2 HDMI, 2 DP, 1 Dual-link DVI).
Guru3D
KitGuru
Techpowerup
Tom's Hardware

MSI GTX 1080 Ti Gaming X TRIO 12.6" length, xx" height (xx" above bracket), xx" width (2.5 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to xxC; fans on with rise to 60C. 2 HDMI, 2 DP, 1 Dual-link DVI).
Guru3D
Techpowerup

Gigabyte Aorus GTX 1080 Ti Xtreme Edition 11.42" length, 5.51" height (xx" above bracket), xx" width (2.5-3 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to 47C; fans on with rise to 55-60C. 2 HDMI, 3 DP, 1 Dual-link DVI).
Techpowerup
Guru3D
ComputerBase (German)
Hexus
Gamersnexus
hardwareLUXX
KitGuru
Tech Report
Tom's Hardware

Zotac GTX 1080 Ti Amp! Extreme Edition 12.2-12.8" length, 5.12-5.31" height (xx" above bracket), 2.09" width (2.5 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to 46-49C; fans on with rise to 50C. 1 HDMI, 3 DP, 1 Dual-link DVI). 320W Power Target.
hardwareLUXX (German)
Guru3D
Techpowerup
Tom's Hardware

Zotac GTX 1080 Ti Mini 8.31" length, 4.92" height (xx" above bracket), 1.61" width (2 slot), two 8-pin PEG connectors, fans always on - min 1400rpm. 1 HDMI, 3 DP, 1 Dual-link DVI). 250W Power Target.
KitGuru

Palit GTX 1080 Ti GameRock Premium 11.42" length, 5.31" height (xx" above bracket), xx" width (3 slot), two 8-pin PEG connectors, Passive fan hysteresis: fans off with drop to xxC; fans on with rise to 60C. 1 HDMI, 3 DP, 1 Dual-link DVI).
Techpowerup
Guru3D

EVGA GTX 1080 Ti SC2 ICX 10.63" length, 4.72" height (xx" above bracket), xx" width (x slot), x-pin PEG connectors, Passive fan hysteresis: fans off with drop to 55C; fans on with rise to 60C. x HDMI, x DP, x Dual-link DVI).
Gamers Nexus
Techpowerup
Hexus

EVGA GTX 1080 Ti FTW3 ICX 11.77-11.89" length, 5.51-5.63" height (xx above bracket), 1.38" width (2 slot), two 8-pin PEG connectors, 1 HDMI, 3 DP, 1 dual-link DVI, 280W power target.
GamersNexus
Hexus
Tom's Hardware

EVGA GTX 1080 Ti FTW3 Elite Gaming (same as FTW3 above with faster memory)
ComputerBase (German)

KFA2/Galax GTX 1080 Ti EXOC10.94" length, 4.53" height (xx above bracket), 1.38" width (2 slot), one 8-pin and one 6-pin PEG connectors, 1 HDMI, 3 DP, 250W power target.
Tom's Hardware

KFA2/Galax GTX 1080 Ti HOF12.2-12.52" length, 5.71" height (xx above bracket), 2.13" width (2.5 slot), THREE 8-pin PEG connectors, 2 HDMI, 2 DP, 1 DVI-D, 250W power target. Passive up to 60C.
Guru3D
Tom's Hardware

PNY GTX 1080 Ti XLR8 OC Gaming11.97-12.6" length, 5.12" height (xx above bracket), xx" width 2 slot), one 6-pin and one 8-pin PEG connectors, 1 HDMI, 3 DP, 250W power target. Not passive at low loads.
KitGuru
hardwareLUXX (German)

Damn you only teasing.

I expect MSI to be good and most of the triple slot coolers, but I do fear higher tdp.... Harder to cool on. I have high hopes on thesi lightning that should appear down the road and the EVGA king pin.

I do havey doubt into weather it's with it or not, but if Vega doest perform as well weight not see a new GPU in more than a year.

What are the chances MK-26 will fit into the ASUS GTX 1080 Ti Strix, and will work correctly?

After all, that video card has two fan headers, which are ready for conventional fans controllable by voltage (less chances of PWM noise).

Asus Strix OC @ Techpowerup added.

Inno3D iChill GTX 1080 Ti X3 @ Hexus added.

Out of lack of custom cooler reviews or very few.... i have been checking rumors and news, and something interesting, not sure if it will matter much or not, but decide worth a share with SPCR since we many like MSI Twin frozr designs.

In past, the changes on the Twin Frozr changes have been more like looks, the cooler itself had minor improvements, at least to what i seen in the past 3 gens, they do have low end twin frozr for the lower tdp cards like for GTX750/950/1050, but the higher end seem very similar always, more was to accomodate the new designs, rgb, etc. But this time it seems its changing in design, the pipes no longer go up/down the card like they used to, now the go sideways like the accelero 4 and gigabyte coolers, that makes the fins go 90 degrees from the past design, i dont think its goign to be huge impact, the cooler gives the impresion of beign thicker, although its still a 2 slot design, again pure speculation, but got me interested.

MSI GeForce GTX 1080 Ti Gaming X Makes a Camera Appearance

From this review "...Near the back of the card, you'll find two black fan connectors that are in sync with the GPU's fans. We have seen this FanConnect feature before, on recent ASUS STRIX cards. Now, it has been improved so that fan speed can be set to a fixed or dynamically adjusted value, according to your CPU's temperature or the higher of the CPU's and GPU's temperatures. This feature requires software installation, though. If you choose to not install the software, the fans will be controlled by the GPU's temperature, just like in the previous version of FanConnect...".

The software is Asus GPU TweakII, the latest version 1.4.3.9 was released on 8 March 2017.

FanConnect sounds like a smart thing.

Seems the first pics were right, MSI has changed the cooler design, weather its better or not only time will tell. Personally i dont like it, as the frontal plate has been abandon for VRM direct touching to the heatsink (in theory should be better), but this will take out the easy to upgrade toward a aftermarketcooler like Prolimatech mk26. Also i dont see memory cooling with the abandoning of the frontal plate. A last thing that i dislike is the double hdmi double dp route, i think 1 hdmi was enough, triple dp was the way to go.

MSI GeForce GTX 1080 Ti GAMING X Graphics Card - Detailed Photos

Catering to the VR headset crowd...

I see your point, but do you need 2? like for two helms?

I think that's the intent. Also, Displayport can be daisy chained..if the monitors have in/out ports.

Asus Strix OC @ KitGuru and HardwareInfo added.

Now it is 2.5-slot desing.

MSI Gaming X @ Guru3D added.

Been trying to find this, and there are some, but very few, and the good monitors i dont see it on them. Seems the GTX1080 will have to work out for the triples screen sim setup or find a manufactuer that follows nvidia reference cards that are still triple dp.

I coudlnt tell by the pictures, but i think you are right, seems slightly thicker.

Guru3D says 51mm. PCI(e) slot spacing is 20mm.

Asus Strix @ hardwareLUXX added.

Asus Strix @ Hexus added.

Guru3d ASUS ROG Strix GeForce GTX 1080 Ti Review

Sadly no reviews from techpowerup of the msi

added.

Asus Strix OC @ ComputerBase added.

MSI Gaming X @ Techpowerup added.

Seems MSI lost their mojo, higher noise levels and higher temps than the Strix. Looking forward to the EVGA FTW3, they were pretty good noise wise last gen, with the exception on going to low on the fans, requiring a new vbios, i think they might tweak this one better, will see. Also keeping my eyes on the Zotac GTX 1080Ti AMP! Extreme.

Also looks like Asus had room to improve...they could have set the thermal target higher than 70C and maybe gotten a few dB quieter.

Yes i think its going to be a great card, i bet they can drop it to Zotac Levels of 29db, the only issue for me, is that its like the MSI 2xDP + 2XHDMI, this will not work out for me, the monitors that ill be buying dont have in and out for DP (only a very few have this), so i need triple DP, seems EVGA FTW3 does come like that, and BHPhoto starting to take preorders for may 11 shipping.... temptations without reviews out ='(



Another that can work out for me is the Zotac GTX1080Ti AMP Extreme, was a quietest GTX1080, so i would expect this is going to be similar, probably a little more noisy as the cooler seems the same and the card runs hotter, but its triple fan and 2.5 slots (although by the picture seems triple slot), just not that easy to get Zotac for me, as the EVGA is also triple DP =)

Gigabyte Xtreme Gaming @ Techpowerup added - with 3 DP just for Abula.

Must be Gigabyte day. Xtreme Gaming @ Guru3D added.

Thanks Steve, seems like a nice card, same noise as the STRIX with the correct outputs, im going to wait to see reviews the EVGA FTW3 (i dont have much hope for this as its only 2 slot card) and Zotac Amp Extreme to decide, both also have 3x DPs.

HardwareLuxx Factory's fastest: ZOTAC GeForce GTX 1080 Ti AMP! Extreme Edition in test

Sadly it doesn't look as dominating as the before Zotac GTX1080 Amp Extreme, according to the review, its slightly noisier and higher temp than the Asus Strix, but not by much, im still going to wait for reviews on the EVGA FTW3 to decide. I wish Asus would have made a 3xDP card ='(

Personally i think MSI should try to do a taller card in the future if they intend to keep with the smaller cards with dual fans, and go for 120mm fans, this would be different and potentially quieter.

Added the Zotac review...kinda narrow fan hysteresis of 46C off and 50C on...

Also added Gigabyte Aorus Gaming @ ComputerBase (and compares against Asus Strix OC).

Gigabyte Xtreme @ Hexus added.