I freeze very occasionally too (what is very annoying because, as I run in fullscreen, and alt-tab or alt-F1 doesn't get me out, I have to re-start the PC). I have a couple of other "minor" issues: total lag in some fights (what is dangerous) and the trainer icon not working after I have been playing for a while (I used to relog in such cases but I've taught that clicking P works around it - this seems to happen also to some Mac users).
Otherwise I am very happy with the new release (I have Ubuntu Hardy, I believe), I think I have never been able to play Planeshift so well since many versions ago (either in Linux or Windows, though this last was probably because my PC was old - from this decade but not the last 5 years).