Davey Winder says that 80 percent of viruses love Windows 7, and that a Windows 7 machine without AV software on it gobbled up viruses like a fat kid gobbles up candy on Halloween. Now this was a bit of an unfair test, not installing AV software, but still, the "we're making Windows more secure" mantra has been going at MS for a while now, you'd think that this would be better.

As a note, here is the article that RoundTop mentioned.