Lots of frustration, mainly. If you ignore the UI issues, Qt for Android works perfectly; I've been controlling TVs and set-top boxes just fine with my Android test device for a couple of months now. But the UI just isn't there yet.

Lots of pieces of the Qt UI are working; most of Qt Widgets work just fine (and even support Android theming to a limited extent); and QML is getting close to complete functionality. But Qt is still isolated from the standard Android UI components: you can't use the layout system, you can't access the Action Bar, you can't create standard Android dialog boxes or use the "toast" mechanism. For me, the most annoying item is that Android's screen hierarchy works in a manner almost identical to Maemo's stackable windows, which is something I use pretty heavily in Pierogi. I hate having to ditch that part of the UI when it should be able to work right out of the box...

I've been trying to squeeze Pierogi into a new UI, with one main window and a lot of dialog boxes. I've managed to cobble together a Qt dialog box that looks a little like an actual Android dialog box, and put together a fake action bar at the bottom of the window. Hopefully, I'll be able to get something usable put together soon...