Excerpt from a detailed review
There are people out there--haters, people who are so invested in Apple products, or Google, or whatever--that will try to convince you that Windows Phone is a disaster. That this product should be avoided at all costs. That it is a tired retread of what Apple first shipped in 2007. Those people, to put it simply, are wrong.
Here's the truth. Windows Phone may or may not succeed in the market place. I have no opinion on that, and believe it or not, I have no vested interest in it one way or another. What I do have is an opinion on the value of this system, an opinion about how it compares to today's leading mobile systems from Apple and Google. And I'm here to tell you that Windows Phone isn't just competitive. It's better. It's more innovative than anything from those other companies, and people will be shocked by how good the big picture stuff is on these devices.
From later in the multi-part review
It doesn't take long to realize two things about Windows Phone. First, Microsoft gets it. In a world of me-too smart phone solutions that all take the same route down application silo hell, Microsoft has rethought how important these devices are to our everyday lives and has come up with something that's not just different, but better. Second, you can never go back. I've often said that the true test of any upgrade, software or otherwise, is how it makes you feel when you have to go back to the previous solution.
And going back to the iPhone after Windows Phone? If not impossible then certainly painful.
Paul Thurrott's SuperSite for Windows: Hands-On with Windows Phone 7, Part 1: Introduction