I personaly LOVE my windows phone (nokia 920). THe os is very smooth and doesnt seem to slow down or get buggy like andriod does with more apps. It also has a very nice and complete ecosystem that syncs very nicely with my windows 8 pc. Everything is very easy to transfer and automatically backup and sync on skydrive. Facebook is also meshed into the phone way more nicely then even IOS does which is hard to beat. Skype is another service that plays nice with the windows os. If you have any specific questions feel free to ask me.
A very well designed UI that is simple and intuitive, but not boring and dumb like iOS. Very, very good Microsoft Office integration, as well, and with Windows Phone 8 a full ecosystem that syncs very well with Windows and Mac.
I had an HD7 and loved it, just wish it had more apps and games, but with WP8 it is a full feature smartphone OS on par with Android and iOS, if not better in some ways (ie, facebook integration, hubs, groups, live tiles/UI, etc.)
Also, easily the best touch screen keyboard I have ever used.