I really like Vista, but 7 does have it's advantages. For one, it uses the winmin kernal and flies. It's noticeably quicker than Vista. Second, it gives you the option to uninstall MS programs like WMP12 and IE8 etc. Speaking of, WMP12 has a ton of cool features. The "play to" and internet streaming are just an example. There are many more things, but those are what stick out to me.
Obviously it's not for everyone, but lots of people will want the latest and in this case, MS delivers strong with a great OS. That's not just my opinion either. That's the general consensus.