I have owned windows mobile devices almost exclusively for years. I started with an XDA, then an MDA compact, XDA Executive, Vario 2, Ameo and Vario 3. I like the customizable nature of Windows Mobile devices and the touchscreens. There is plenty of software out there, but for my Internet, Email and Multimedia needs Symbian has more to offer. There is more 'fun' stuff available for Symbian.
Also to call Windows Mobile devices 'powerhouses' is nonsense - The T-Mobile Ameo was supposed to be a powerful device, but multimedia playback is vastly inferior to Nokia devices. My N95 could playback ANYTHING using the coreplayer for symbian application and the browser is better.
The Vario iii is quite nice to use, but my current device - the E90 is streets ahead since not only does it have a better browser, better multimedia playback and more shortcut buttons, but also a MUCH better screen. The front screen on the E90 alone is the same resolution and has more colours than the vario iii. The E90 is also much snappier and more convenient to use as a phone. Windows mobile is often glitchy when it comes to call handling and texting.