Not a 3d game of course but a simple 2d game, a side scroller or puzzle game, and PyGame seems like a nice way to keep things simple.
So for me I'd love to hear about what kind of performance people have been able to achieve using straight PyGame, and whether or not it makes sense to try this...
Quite a number of such games have been written, and they seem to work just fine. Check out the games on the Pygame web site, or the PyWeek competition entries. Many of them have arcade-type action that works very smoothly.
Puzzle games are even easier, since speed isn't usually an issue at all.
-- Greg