I've had my HTC HD7 since mid november, and I have to say i love it just as much now as when i first upgraded to it, if not more. The UI is fast and intuitive, I've found apps for most things that I would want, although they can are very expensive in some cases. I'm never going to pay £5 for a train app, although I can see that it would be very useful.
There are some very good games for it, which I have enjoyed a lot - Rocket Riot for one is lots of fun. I'm even making extensive use of zune, and a years zune pass. I've listened to and enjoyed more new music recently than I have in a while. It's great remembering a band and thinking i'd like to listen to it and then going to the market place and downloading it to my collection to listen to immediately.
It's even good for the staple phone tasks of typing messages and making phone calls. I think I more readily reply to my girlfirend because it's a pleasure typing out a message compared with any of my previous phones and much quicker too.
But you might have seen this coming and there is a big but, my experience of the WP7 platform on the hd7 hasn't been entirely smooth. On average I have to restart the phone every couple of days because an app stops loading, or in some situations the graphics go very glitchy. This isn't a massive issue because the phone restarts and is useable in 1-2 minutes, but should I have to put up with this, or should I get onto o2? I've put up with it so far because I half expected it being an early-ish adopter and there's supposed to be an update in the next month or so which I'm hoping will fix the software issues. So for now i'm putting up with these issues, because the rest of the time my HD7 has been awesome.
All in all i'd recommend it to anyone, a few people in the office have looked at it and liked it. I the company I work for is thinking of using WP7 devices as work phones. Which I can understand because of the office apps and the ease of setting up outlook.
How are other people who have taken the plunge finding WP7? Good, Bad or just indifferent?