I have had couple of really bad experiences with Windows Mobile over the years ... remember my 90000 paper weight.
Anyways this are a million times better after getting the HTC Fuze. right now i'm super excited about the Windows Phone (or can I call it the version 7). I'm using WinMo 6.5 at the moment with couple of custom applications from Resco and things are nice and smooth. Looking forward for the new and exciting stuff planned for the next major release of WinMo.
Despite all the ups and downs one thing I love the platform is the support for developers to develop apps. This time things are taking a much cooler route by adapting Silverlight into the core UI of the Phone. So ... Developers who cant wait to get their hands on the new device ... goto http://developer.windowsphone.com/ to get started.