I switch phones a lot (cellphone junkie lol) but have been using WP7 and now WP8 on and off since it debuted in 2010 and originally started with a Samsung Focus. Always had that feeling that Microsoft had something special with the WP OS. I have watched this platform grow, and slowly mature and although it definitely has room to grow, with WP8, its most definitely a great OS, and a great alternative to Android and iOS.
Anyways...to answer the question, I moved from a Lumia 900 to a Lumia 920, and very happy with it so far.