NVIDIA crash issues are still being investigated
The PC version of Tomb Raider has been patched recently, resolving an issue with a basecamp UI glitch, and bringing in some appreciated GPU performance improvements. Eidos states that if you just want to test this patch, there's a beta version available on Steam (Build742.0) that you can revert back from. Since a prior patch actually brought the basecamp glitch along with it, it might be a good idea.
Eidos also reports that there's not a solid fix yet for people who are experiencing crashes on NVIDIA machines, but "some progress" has been made, and an update will be provided soon. PC issues aside, Tomb Raider is a great game, and if you haven't already, you should really check it out.
Tomb Raider PC Patch [Eidos]