Just to add; and through the Haxe NME framework it compiles to Android and iOS targets.

Haxe itself is pretty solid and is gaining steam almost every day now.

NME is not as easily recommended. It has very high coverage, and it's shipped a few products as demonstrated in the showcase, but the build process still shows immaturity; the Flash target is wonderfully consistent, but other targets remain pretty fragile. The general trend is "better with time" though.

Haxe is nice, but it is still not as transparent as one could hope. The differences in the way its various targets work make this understandable. Still, it still isn't "code once, run everywhere".

The main problem seems to be flash is really directed to pixel/bitmap manipulation. While on cpp/OpenGL that is extremely slow, and you have to use something like a Vertex Buffer Object.

The end result is that you probably will still have to keep two (at least) separate rendering paths if you want to support all targets.

That being said, the fact that the mobile platforms (android and iOS) are the same target (cpp), together with desktop (osx, linux and windows) makes it a very nice platform for developing a game. IMO the html5 target is the weakest link at this point.