Right now it is still very basic, however it handles certain primitives for you quite well. Animations are implemented for you using tiled images (this is where you put all your frames into a row/column in a single image) which is very handy and much better than using animated .gifs. It will also do the preloading for those animations so that they don't need to be done during the gameplay. There are also mechanisms for grouping different animations into layers so that you can have different background/foreground groups, sprite groups, etc.
There's also some nice little addons for the game loop and input handling.
Other than that, there isn't really much to it. It has sound, although it is experimental and is not guaranteed to work (I haven't tested that part out yet). Supposedly it has collision detection, but it doesn't seem to work for me. Maybe I'll fix it and submit a patch.
I've been expanding on it a lot, I've made up two view classes that handle a scrolling background. You can either just straight up scroll by calling scroll(dx, dy), or you can have a "locked view" where it follows a particular sprite (it nicely handles the edge of the screen!).
I've also built-in a more efficient object management system using quad-trees, which are a space-partitioning data structure. It means that when you do location-dependent things like collision-detection you don't need to query every single object in the game, you just need to update the visible ones. This might also be good for animation rendering since you wouldn't need to update animations that are not visible.
Anyway give it a shot if you like, but remember that it is still pretty alpha! And don't bother with IE since it is really too slow for something like games.