My brother and I decided to build a HTPC. Having all media and games (well not all, but a lot more of it) in the same place, within easy reach, is awesome. The build is near perfection, with only a few small "bugs" left to sort out, such as a the screen flickering now and then, sometimes losing colours, something which I have yet been unable to find the cause of.
And the connectivity of the mouse and keyboard is less than desirable. I'm buying the Logitech Wireless Touch Keyboard K400 which hopefully will sort that out. Looks pretty neat, that one.
The media-side is "powered by" XBMC, a superb piece of media-center software that looks and operates just delisioucly. :-)
Games.. Well, the current-gen gaming will still be "left to" the consoles we have (Xbox 360 and Wii) but [more interestingly] various emulators will take care of the older-gen (Nes and SNES and the like). Using a wireless gaming reciever we're able to play with the 360's controllers. It's not always optimal, but beats the hell out of using a keyboard. ;-)