I just recently bought the HTC Radar 4G on T-Mo and it's my first experience with WP. WinMo was complete rubbish (my TP2 is pretty much brand new in the box) and I thought I'd never try another Windows phone. The overwhelming number of 5-star reviews on T-Mo of the Radar made me curious so I snagged one for a good price.
I'm pretty impressed. I started of with BB from 4.5 onto 5.0, had an iPhone, then had an Android (still had my BB though) and finally upgraded to the Galaxy S II as my only phone.
I found Windows Phone to be very responsive and it just works. I was initially turned off by the lack of customization (I've rooted my Android phones and like to customize them) but got over that once I started using the phone.
I think WP has a bright future ahead of itself. It's the perfect OS for those who just want their phone to work. I don't understand why people get so worked up over things like their phones' OS -- as long as we're happy with what we have, it's all G. I love that my Galaxy S II on Android is setup *exactly* how I want it with widgets, wallpaper, apps etc.. But I also love the simplicity of my Radar on WP.
Castrol EDGE 5W-30 is my drug of choice.
Toyota | moving forward
Primary: Galaxy Note II & iPhone 5 (AWS): 5 lines, 1x $15 4.5GB data, 3x $2.99 T-Zones (truly unlimited 4G data), myFaves, corp discount + $10/mo loyalty discount = $88/mo tax inclusive
Secondary: iPhone 3GS: Airvoice Wireless, Samsung Fascinate & HTC Trophy: Page Plus