I tried under the same conditions as you (5 bots, 1 human, large dirt patch, score limit 300) and never dropped below 60 fps. I tried again with some more ridiculous conditions (13 bots, 1 human, large dirt patch, score limit 999, weak spot), and while my framerate wasn't great (mid-30s), it didn't vary enough to cause notable jumps. I kept an eye out for evidence of memory leaks, but the only place that could be possible is in the way I allocate space for replays, and everything seemed to be managed quite smoothly.
In those crazy conditions I hit up the debug panel (obviously not available in the release version) and saw script execution was taking up a whopping 10 ms -- I'll have to optimise my collision function, I think, with some sort of means to eliminate collisions that aren't going to happen more quickly. It'd be a shame for CPU performance to be such a bottleneck, even under the worst conditions.
These are my specs: Intel Pentium D 3.00GHz 3.01GHz 4 GB RAM 32-bit Windows 7 GeForce 9600GT
But I couldn't find any reason for (nor evidence of) jumpy performance. There's the slightest possibility it could be happening in v0.1.4 and not v0.2 (since now I'm working on v0.2), but I seriously doubt that since the only changes I've made so far occur out-game, in the menu.
