Owned one. It was a damn good phone, had a great UI that remains unsurpassed to this day, but it clearly came at least two years too late to gain the critical mass needed for a thriving ecosystem.
I loved the UX on it too, but the crappy locked-down web browser killed it for me.. I don't even use apps, but since I couldn't load Firefox with uBlock on there, and there weren't any single-purpose apps, it was really rough