Well MS always had good development tools.
The main problem is that their OS were never reliable or performing. I was very pleased when I found a sucker to sell my last Window based mobile that and slow as hell (when not crashing).
So I am quite sceptical if Windows Phone 7 will be stable and fast as it seems Microsoft rushed them out to its stop market erossion from iPhone and Adroid. I will wait for a SP1 I mean Windows Mobile 7.1 before considering a Windows mobile again.