I actually have a few setups:

REAPER on XP
SONAR on Win2K (yep, still running that!)
Garageband on Mac OS X

Believe it or not, I'm getting studio-quality tracks with Garageband. I think the stripped-down features actually encourage better recordings. I was planning on upgrading to Logic but now I might not bother.

I have an assortment of mics but my faves are just a Shure SM57 and an AKG condenser.

I use an M-Audio FastTrack Pro as the interface. It's...okay. Preamps are a bit more noisy than I like.