How's my specs
2 x 2.66Ghz Quad Xeon's (8 Physical Cores in total)
Edit: Overclocked to 3.2 Ghz
12GB DDR2 800MHz
2 x 60GB OCZ Vertex 2's RAID 0 - Mac OS X 10.6.4
2 x 64GB Crucial C300 6Gb/s SATA III RAID 0 - Windows 7 Pro 64bit Boot
2 x 300GB WD Raptor RAID 0
Sapphire Radeon 5970 + 5870 Trifire
Blu-Ray R/W
Yes it's a Mac, and Yes it runs games perfectly, like 100fps av on Crysis...
All together it cost about £2,000 so gaming on a Mac is perfectly do-able if you put the effort in...
I use Mac OS X Way more than I use Windows, but if every I want to do some gaming I turn it off, about 27 seconds later it's on again ready for me to do some gaming...