As one example of its shortcomings, Pygame doesn't seem to support hardware rendering and the maintainer seems to think this is an advantage [ http://www.pygame.org/docs/tut/newbieguide.html ]
Edit: To be clear, you can make games in vanilla kivy just fine (and it's probably much more performant than pygame), but kivent is a dedicated game engine with more efficient graphics internals and nice things like chipmunk integration.
I wish bundling Python was easier. I read this morning in the Kivy docs that you can't even bundle python 3 at all yet.
Many years ago a friend of mine wrote a Python binding to the PopCap engine. It was so great, the exe and the script. Thats all you needed and you could just whack those two things in a zip and you're done.
I suppose I just picked up on the writer's ceaseless discouragement of using hardware rendering and interpreted that as a sign that it didn't support it instead of fully reading what was written.