Oh and on the learning to write bit. Android code is mostly Java (there are ways beyond my ability to compile native code for speed but it's rarely needed).

From my own VERY LIMITED dabbling, I think the hardest bit I've encountered to get used to is its sort of asynchronous nature. You mustn't and in some cases can not tie up the UI. If a job (eg. my print program which was once on the play store, which does a few network tasks), you need to put things out to another thread or use AsyncTask. It's sort of start something going and wait to get notified it's happened rather than simple "straight line" and I find that can be difficult to get my own head round at times.