I played a vast amount of game titles and also experienced the testing phase of the XFX 8600GTS first hand. This involves a mass amount of time investment and really gives the users a good feel for how well the card plays games as well as how stable it is over a period of time. Performance on the card was better in most cases than ATI's competing products in the same price range, but with the advantage of DX10 support the ATI solution begins to pale in comparison. This may at this exact moment not have much relevance on your gaming experience, but as DX10 becomes a reality this alone would be reason enough to buy the 80 series cards for anyone serious about their gaming.
FPS games are always the titles that push the envelope as far as technology advances go and I played FEAR, Prey, SIN Episode 1, Stalker and Tom Clancy's Rainbow Six Vegas for many hours. These titles were all playable at the 1680X1050 resolution my monitor defaults at and only had problems like staggering when the effects and AA turned up to their highest settings. Most games still run a bit faster in the XP environment, but drivers are getting more robust and stable all the time in Vista so that should change very shortly. A few of the games had major loading issues using Vista, Prey and Supreme Commander were so slow to load in Vista in actually took four minutes for Prey to even show the play menu. Supreme Commander showed the same thing and was quite sluggish in Vista as well. As far as RPG/RTS games are concerned the 8600GTS plays them all without error or problem except where listed. C&C 3 played especially well as did Jade Empire in both XP and Vista so anyone who plays these types of games will be more than satisfied with the cards performance at all levels and resolutions.