Have you actually used one?
To all those who spurt out paragraphs from the usual MS hate script - have you actually had the opportunity to use a WP7 for a week or so? After you get over the lack of 1990's 3d icons etc..., it turns out (from my experience) that the UI and indeed the whole phone experience is actually pretty bloody slick and not that bad at all.
Once you start connecting stuff up with a windows live account etc.., then I'd be surprised if any other platform can demonstrate to me that level of integration and connectivity (e.g XBox/ZunePass/Skydrive etc..). The hub centric approach that WP7 employs actually starts to make sense once you start playing with it - so much so that going back to traditional paradigms on other smartphone OS's leaves you feeling of being short changed.
As a dev, I've also had the opportunity to use the new Mango build for a few weeks now and that just adds a whole raft of new stuff. In particular the People is just absolutely nuts and a great idea (one of many small improvements that taken as a whole give it that rev2 polish).
What I do have a problem with however is Microsoft's complete lack of decent marketing for this platform. Can anyone remeber the last time they saw a WP7 ad on UK TV? Last one I saw was probably Q1 during an XFactor break (disclaimer - I don't watch that shit, just happened to see it during channel hop).
So, at the moment we have a great platform but a completely useless marketing message from Microsoft.