I've played with WM6 and agree it is a bit better, especially the phone dialler, which is now merely annoying rather than almost unusable. And the improvements they talk about for WM7 and beyond do sound like they at least acknowledge some of the more dire problems.
The Exchange sync security features are indeed fiendishly intrusive. I had to disable it after a week or so as the absurdly small screenlock timeout caused me too many problems, which thereby negated the main justification for replacing our perfectly functional non-3G Nokias with the HTCs in the first place.
What I'm getting at is that MS buying Danger and giving itself a way out of the whole Windows Mobile mire makes a certain amount of sense to me. They can have something that's still MS branded, leverages all their proprietary systems and services, but which is designed by a team that don't actively wish pain and suffering on their users.