I used a WP7 for several months last year. In many ways I really liked it, the UI was pretty slick, live tiles where great, the whole thing was surprisingly polished. But I now use an iPhone. The reason is lack of quality 3rd party software. The PDF viewer available for WP7 (there was only one) was absolutely abysmal. Very poor UX. And that was all to often the case. Where Android or iOS would have numerous great app…
The 3rd party app criticism is in my view an outdated one. One year ago would have been premature to make a declaration on the availability of 3rd party apps for the Windows platform since it was still relatively new. Windows Phone has been catching up and can probably do so more quickly now that the phone and desktop OSes can use similar code. Edit: Since I am being downvoted for my opinion, I will add some evidence…
You can't expect a user to stick with an incomplete platform when there is viable competition, based solely on promises that the situation will improve. In fact, since Microsoft has announced that current Windows Phone 7 hardware will not run Windows Phone 8, anybody who was counting on their phone getting more useful over time has been proven to be a sucker.