I am fairly happy with AppGameKit, but there are issues still. Such as my adverts don't display on android, at all anymore. Sound is ropey on android also. I'm sure all will be fixed soon, or at least I hope so. I'm sure there are other issues on other devices I have no idea about, all these need getting working before new stuff is added.
I'm all for improvements, and shaders could be pretty nice. Probably much more likely when the 3D engine is introduced though than beforehand. In fact I would probably expect it in a 3D release.
Unfortunately for the advert bug, I see no workaround apart from a total rewrite of the movement and scrolling code. Not a task I fancy much at this late stage of development. I am hopeful this particular bug will be squashed in the next couple of days.