I'm impressed with Windows 7. It's the first OS MS has come out with in a LONG time that's worth looking into. More stable and having less requirements than Vista, 7 is the first OS that can legitimately compete with Mac OS. This isn't to say I'm writing off Mac OS, but Apple needs to watch this particular version of Windows, whereas they never had a concern before.
Regarding Snow Leopard; I remember a Microsoft rep being asked why Windows updates cost $100+ but Mac's latest OS release costs just $30? The MS rep replied back that the newest version of the Mac OS (Snow Leopard) wasn't a true update to the Mac OS, that it was more of a behind-the-scenes update and that MS calls those kinds of updates "service packs" which MS does not charge for. He said it pretty smuggly, but I thought, "Yeah, Microsoft CANNOT charge for their service pack updates because their OS is so buggy. If they did charge for SP updates, they'd go out of business because no one would pay for them."
With that aside, Snow Leopard is a good OS, too. It's coming down to the wire for both platforms. The competition is heating up.