Started acquiring parts for this last year, just finished building it about a month ago.
I game on this guy, and so far I've encountered no problems. I've been able to play every game I've tried on the highest settings with no lag, save that of Crysis 2 and Far Cry 3. I play mostly older games/less graphics intensive and have been totally happy. Also, listening to music, watching movies/tv shows, etc etc.
Totes McGotes happy I did this, have a feeling I'll be using this for a while :)