I use this rig mostly for playing wow, so the GPU is not too big of a deal though I do plan on upgrading it when the next generation comes out. I have replaced the stock cooler that thing was extremely loud and I now have a hyper evo 212, it is much quieter and have added a second fan to it. The PSU is a low end off brand I plan on replacing it here soon, but it has been trucking a long fine for the past few years (it came from my previous rig).
Issues: The front (top) USB 2.0 ports were bad, NZXT send me a replacement part and all has been well since. The Hyper evo 212 was a pain to install, but that is normal with this kind of cpu cooler. The mounts for the extra fan for the Hyper evo 212 are not as snug as I like, but I don't have any issues with vibration or anything like that. The PSU leads were not long enough to run behind the board, so I had to pick up an extension.
The rig runs WoW at ultra settings at around 80FPS with little issues.
I played Diablo III at its highest settings and the PC did not lag one bit.
SC2 runs at 200 fps in the menus and cinematic, and 60fps in matches on top settings.
Skyrim runs at 60fps on its highest settings, I cannot get it to go above 60fps. My guess is it can detect my monitors refresh rate.
Counter Strike: GO runs like butter, no hiccups or anything.
When streaming there is no performance impact to games not matter what speed I encode at.
As far as windows goes, 7 second boot times everything runs really fast. Nothing really to note here.
I cannot seem to get the thing to run hot no matter what I do, which is a good thing.
***Edit I have replaced the PSU with a Corsair 500w PSU, I don't plan on crossfireing or SLIing anytime soon so I don't need a really high watt PSU. No issues with the installation and it working like a champ.