According to the Ad trade press, Microsoft felt that they were being "defined" by the Apple ads and wanted to claim back their identity. However, just by having a bunch of different people tell you that, essentially, they use PCs seems, well, besides the point. Everyone knows that most people use PCs. So what's the news here? They're not really telling you why using a PC is better. But that's exactly what Apple does in its ads. They give you proof points in each ad as to why switching to Apple is better than continuing to use a PC. That's why the campaign has been so effective.
These ads remind me of the Dell "Portraits" commercial that an agency called Mother created, in which you see different kinds of hip, young kids carrying their Dell computers around set to the Kira Willey song "Colors." The difference is that the Dell ad feel fresh, young and hip, while the Microsoft ads feel kind of ordinary and not particularly memorable. Here's a link to it on YouTube:
http://www.youtube.com/watch?v=TCwKndz41P4
BTW, if you go on msn.com, they have an online execution of the campaign, with many of the testimonials from the ads, plus more, that appear surrounding their normal interface after you rollover their ad. It's a cool execution. Too bad the concept behind it lame.