I don't know that much about Windows Phone 7 but my understanding is that developers code against a version of the CLR, so their apps should be easily ported to a new OS.
Yet another Microsoft attempt at mobile? If they screw Windows Phone up, I doubt they will get another chance from the public.<p>Microsoft is good at one thing: backward compatibility, if they throw this away, I don't know if they will have enough value remaining in their offerings.<p>I really think Microsoft should either man up, and create a descent mobile OS, or simply stop creating new crap every once in a while.