OpenGL ES.

As mentioned previously Qt is very well supported in Meamo5 (all systems have quirks of course) and it's not wildly different to a desktop environment - there are a few bits to pick up on your travels - so if your comfortable with Qt you should be fine with it. As Meego has Qt at it's core as well it's a good route to go development wise.

But you aren't just limited to Qt with c++, python support is good and well used, Gtk is accessible with c, c++, python and vala too. It's a fun device to work with, not too easy that there's no challenge, not too hard to completely put you off.