Lex Friedman of Macworold recently spent a month using a Windows Phone. It's a multi part series of articles where he talks about aspects and features he likes about Microsoft's mobile phone operating system. I won't spoil his final verdict, you can read all the parts of his series at Macworld.
I think it's important to see what else is out there. Although I prefer Apple's offering, it doesn't hurt to see what Google's Android and Microsoft's Windows Phone offers. For some, these other platforms may provide a better solution depending on our needs. Lex's month long trial with Windows Phone is a well written experience of Windows Phone from a iPhone user's perspective.