Windows Phone was great. I'd done Windows Mobile since 2005 and it was nice to be able to continue developing with C#/.NET and Visual Studio (back when it was still good) in a more modern OS. One thing that really spoiled me permanently was being able to compile, build and deploy the app I was working on to my test device effectively instantaneously -- like, by the time I'd moved my hand over to the device, the app was already up and running. Then I switched to iOS where the same process could take minutes, also Blackberry where it might take half an hour or never happen at all.

Funny thing: RIM was going around circa 2010/2011 offering companies cash bounties of $10K to $20K to develop apps for Blackberry, since they were dying a rapid death but were still flush with cash. Nobody that I know of took them up on the offers. I tried to get my company to make a Windows Phone version of our software but I was laughed at (and deservedly so).