I had the top-of-the-line Nokia Lumia 920 (designed just before the acquisition), and the plastic case was too soft and collected dents & scratches like crazy. The matte finish was also too slippery to hold onto (I ended up putting some skateboard tape on it).

OTOH, I found the Windows Phone operating system to be highly responsive and I was able to navigate screens more quickly than the previous iPhone or the current Android I have. The problem was that as third-place in the market, few apps were available for it, and those that were weren't being maintained.