Phil, Win Phone makes sense for you to develop on, you're a Windows developer. I haven't seen one so I'm no sure how nice the UX is.

I do know this. C#/.NET is one fantastic development platform. I have yet to experience the productivity in Objective-C/Cocoa that I have with the C#/.NET combination. I'm getting better, but I have a long way to go.

In the end it'll be good for the mobile economy; choice, lots and lots of choice.