Apple iPhone must be included in any survey of SmartPhones.
HTC is one of the leading vendors, and they use Windows Mobile Operating System.
A colleague is using the HTC Titan which looks good.
It has a slide-out keyboard which is much better thann using a stylus.
I have been using a Mio DigiWalker for over a year with good results.
The Nokia N96 has just been announced which will take up the iPhone challenge.