My experience (to address the balance a bit)
Windows 7 Ult x64.
Been running the H80i for 2 weeks now, no rattle/buzz, thought these fans can be noisy at full speed. I'm currently running it 24/7 on a 1090T based folding machine. Flat out at 100% with the fans locked down to 1400rpm my cpu temp is 35C. Running IBT the temp doesn't go over 40C.
The issue I'm working on for myself and others over at the corsair forums is the ***ppy drivers corsair bundle with the software. I had to force these drivers to install (the hardware ID is different to that in the driver inf file). Once you get them installed there's the dreaded '!' triangle in device manager, (code 10) fails to start.
I reinstalled windows twice in an attempt to get them working, suffice to say I wasted a full day on it.
I've finally got the dashboard working properly by refusing the offer to install the unsigned drivers. Went through Windows Update and it installed microsoft's drivers. reboot and the dashboard is working and I have full control. WTF!!
The H80i is now installed as 2 devices, a 'USB Input Device' which i presume is the interface and a 'HID-compliant device' which I presume is the H80i itself.
But the software works fine with these drivers.
It's worth a try, at least to verify if you have a driver or hardware fault. It's not gonna fix everyone's hydro, but it will fix some.
Hardware IDs:
Hydro itself - VID:1B1C PID:
0C04
Drivers - VID:1B1C PID:
1C00
I'm a happy bunny! Good luck peeps
*edit*
Even went to Silabs for their version of the drivers, same hardware ID issue!!
It rings true that most of the info you see posted on forums is the bad news, you hardly ever see anyone posting 'It's FAB'!!