On my Gigabyte UD5H+i3770K, Windows 8 Pro and USB 3.0 microsoft driver is not working properly.
Back usb 3.0 ports work fine (VIA). But all the other (internal USB hub's) work with USB 2.0 speeds. On Windows 7 USB 3 were all good.
Propably there is some bug with Microsoft USB 3.0 eXtensible Host Controller. I dont know if the problem is with VIA VL810 or is the intel. I think it's Intel chipset usb, and VIA is working fine. But there is definitly some bug with Microsoft Extensible host controller. On Windows 7 with Intel® USB 3.0 eXtensible Host Controller Driver version 220.127.116.11 everything was flawless.
So basically Microsoft USB 3.0 driver works for some ports and not for others. Still buggy. Works on 4 of my 10 USB 3.0 ports...