I got Vista a few weeks back, and have found it nothing short of delightful. No compatibility issues, no performance downgrades, none of the complaints I've heard PC gamers cussing over for the past year or so. Then again...I've been playing Oblivion and the Battlestar Galactica mod for Homeworld 2, so I haven't exactly been pushing the OS to its limits. If you're playing things a little more current, and are finding things on Vista a little slower than they should be, chin up: some benchmarks run by ExtremeTech have compared Vista's SP1 to XP's new SP3, and found that over three games tested (World in Conflict, Supreme Commander and Crysis), Vista was just as fast as XP on two, and marginally faster on Crysis.
Gaming Performance: Windows Vista SP1 vs. XP SP3 [ExtremeTech]