We've heard a lot of developers in the past speak positively of working on Windows Phone 7 (and some who have not). Fairy Engine, who make Jigsaw Guru and Jigsaw Guru Free, have had an interesting experience so far with their game actually not doing so well, nor getting much attention (sorry!).
Despite the lack of enthusiasm though, they still have high regard for the new OS. In an interview with Electronic Theater, they had the following to say:
"I'm not saying everything is perfect, but Windows Phone 7 is a very pleasant platform to develop for."
Other areas they liked were the submission process and writing in C# and XNA. They also do have plans to bring more titles (unannounced) to our OS in the future including an Xbox 360 version of Jigsaw Guru. (Electronic Theater will post the full interview tomorrow) Goes to show what having a good developer ecosystem can do.
Speaking of that game, while jigsaws are not our "thang" so to speak, it actually is a nifty little gem--especially how you can use any photo on your device that you took as a jigsaw puzzle, ranging from a few pieces to a whole lot. It should keep jigsaw enthusiasts busy for sometime. They also seem to be having more success with the free-but-ad-supported version over the pay, a similar trend we've seen with Impossible Shoota (review) and that developer.
Grab Jigsaw Guru Free here in the Marketplace, for those interested.