Software update from 10.6.5 to 10.6.6 worked fine on my GA-P55-USB3 (rev. 2.0) with F8 bios (haven't updated to F9 yet but will soon).
Sound (macman's unified realtek driver), graphics, network (lnx2mac), usb, all seems to work fine so far.
I haven't tried the App store, but reckon it's a good idea, other operating systems have had it for a while (at least for free programs), and there have been 3rd party solutions, but this is a proper solution - good for the user IMHO. Bad for some dealers I guess though. (I'm amazed there is still no app store for Windows)