In case anyone still tempted or wating for the STRIX, even though this is not the upcoming 750ti, but a 780 and will release more heat, there is an interesting review from TechPowerUp ASUS GTX 780 Strix 6 GB
Now for the ASUS STRIX's unique feature. As long as temperatures are below 60°C, the fans will not engage, so there is no noise, which is awesome if you work all day and only game rarely. There is no fan noise to distract you as you work. Once you fire up a game and temperatures climb, the fans will engage once the GPU reaches around 65°C. So the fans might not even engage if you play light games.
Once the GPU exceeds 70°C, the fans ramp up very quickly, though, and end up relatively noisy during gaming. I'm not sure why ASUS chose such an aggressive fan profile, but it seems to run the fans a bit too fast in active mode. This may be a limitation of the STRIX technology.
I'm not sure if the noise difference is worth it compared to a quiet GTX 780 unless you are a low-noise freak. The quietest GTX 780 we ever tested is MSI's GTX 780 Gaming 3 GB (the 6 GB version is noisier). In idle, MSI's card obviously spins its fans, but it is also so quiet that you will not hear a subjective noise difference to the ASUS STRIX with its fans at a full stop.
With just 30 dBA, which is just a fraction of the noise the ASUS STRIX produces, the MSI is also very quiet during gaming.
Lets hope the less heat the GTX750ti might make the strix version work out better than the gtx780 or maybe Asus can revised their vbios fan profile, that has happened before with the GTX780 DCUII
Update: ASUS sent me an updated BIOS that improves gaming noise levels of the card dramatically. NVIDIA's Boost 2.0 tries to manually adjust fan speed levels to avoid sudden changes. ASUS did not take this mechanism into account, so the card ended up running higher fan speeds than intended. With the new BIOS, the card reaches 72°C under load (good), and noise levels are reduced by 6 dBA (very good). You can find the updated BIOS here, but it will also be included on all retail cards.