The important thing you forgot to mention is how does it sound?
I got the X-750 yesterday and plugged it in with only GPU fan running. Harddrives and optical was disconnected except the SSD. It was dead silent in idle from 20 cm distance. If I put my ear onto the PSU, I could hear a faint sssh sound like a gas leak. No coil noise and such that I was afraid of.
I connected everything and booted the machine into windows. The fan doesn't run in any idle operation, so I opened MSI Kombustor (MSI's furmark) and it took 4 minutes into Kombustor with 1920X1200, 8X AA, stability mode and extreme burn before the fan started. At first, it made a very low noised TTJUGH sound, like it haven't decided if to start or not, then, when the fan stabilized, noise went away and it was inaudiable from 20cm in my setup. The noise didn't rise above my ambient sound and I was listening directly to it (I have a Thermaltake Mozart TX cabinet, where the fan is in its own compartment. I was running Kombustor for only 10 minutes and when I hit ESC, the fan went off immediately.
The X-750 I received had a plastic fan air deflector positioned near the outtake of the PSU. I recon its made to push air back into the PSU before it goes out. I listed and couldn't see that there were any distortions in the sound or turbulence noise coming from it when the fan was running.
All in all, I am very pleased with this PSU!
My system is:
Powercolor 5870 PCS+ (with custom fan profile)
1 SSD harddrive for OS
1 1TB harddrive for games
1 DVD burner
2 case fans (Noctua NF-S12-1200 on fan controller at lowest speed)
1 Noctua CPU cooler with Noctua fan controlled by silent settings in bios
Thermaltake Mozart TX case modified after all the rules I could find on SPCR