OP: Did you ever find a satisfactory fix? I have a new 2015 model of the XPS15 and I also got these crashes.
The following seems to work, for me, for now, for at least the last few days:
- Install the NVIDIA driver though Menu -> Administration -> Driver Manager
- Run Menu -> Administration -> NVIDIA X Server Settings (should be installed alongside the driver, otherwise it's the package nvidia-settings installable through your favorite package manager)
- Use that settings tool to choose the GPU profile "Intel (Power Saving Mode)"
You only need to do all this once, the settings are saved. My system has been stable for a few days now. The Intel mode should also be better for battery life. The downsides are (a) presumably, less performance on 3D-intensive games, and (b) the settings manager is slightly broken, so switching back to the NVIDIA GPU seems to require purging all your nvidia-* packages and reinstalling them. But so far I'm fine just using the Intel GPU.
[Edit: The nouveau driver did not work for me, it was unstable. It even crashed the whole system when trying to switch to a virtual console.]