Is Windows 7 or Apple's New Mac OS X 10.6 (Snow Leopard better)? Both of them are moving in the same direction - an intuitive Operating Systems. Aren't we all sick of stuff that does not work?
Just calculate how much time you waste on a daily basis trying to figure out things. You just want them to work, not caring about technical details.
Snow Leopard is way faster than any previous Mac OS and is considered a clean up release. When installing it 6 GB Disk-Space will be freed as they get rid of really old code.
For Gamers wanting to play something except Blizzard games OS X 10.6 is still no alternative. You'll need to go for Windows 7. If you are a gamer Windows is the only OS to go for.
(And yes, you can install Mac on a non-mac computer)