Loving Windows 10 Mobile so far and I have no plans to go back. However, it did seem to lose my phone numbers (at least, the ones I had manually entered from my old tracfone and actually cared about). The GPS navigation seems to have a lot more options, Skype now seems built into the OS, and most importantly my little physics game runs on it. But to say it runs slowly is an understatement. The physics plugin may be too demanding for the demo I have on this site (10+ objects), or perhaps simply limiting the app to 256 colors would speed it up. More thoughts on Win 10 later!
Got Win 10 Mobile up and running