My favorite WinMo Device so far is my current, it's a AT&T Tilt (HTC Kaiser). As for a recommendation I would stick with a HTC made device, because they are so easy to modify (see XDA Developer's Forum) and also I would definitely go with a WinMo 6 compatible device with touchscreen. However, I would also go with a device with a Hardware Keyboard. As much as I like touchscreens nothing will ever replace a good tactile keyboard.
On another note I can't wait for the HTC Touch Pro to hit stateside and the rumors are that it's going to AT&T to replace the Tilt. The Touch Pro is the same as a Touch Diamond with 2 big exceptions; It has a sliding keyboard and it has a MicroSD Slot instead of internal memory.
As far as software WinMo by default has great functionality with the exception of it's browser. I currently use the 'SkyFire' beta browser which has all the functionality of the iPhone Browser. I tried the Opera Mobile 9.5 beta, but it's way to buggy right now, maybe when they clean it up some more it might be ready for prime time.
I've also tried the SideShow beta and MediaCenter Gadget beta, they both work fine, but the UI really needs some work, hopefully the final version will fix these also.
Dwight 2001
Vista Ultimate
E6600 Core2 Duo
ATI 3650 256MB
2 GB Ram
bGears Enspirer Sound Card
Pioneer BDC-2200 BluRay Drive
XBOX360 HDDVD Drive
Sony XL1B2 200 Disc Changer
1.5 TB Storage
HDHomerun
Linksys DMA2200
XBOX360
It's all good