Recently bought a Dell Precision M5510 that comes with Ubuntu preinstalled. Aside from the various linux-specific issues I noticed characters sometimes appearing twice when typing on the keyboard (external keyboard works just fine). A quick search tells me this is an issue with a whole range of Dell laptops; they've been having these problems since at least 2009. The popular XPS 13/15 models are also affected. My keyboard has been replaced, to no avail. Now they want me to send it in, but reports on their forums indicate that doesn't get it fixed either.
This is a warning to all coders/fast typists here: stay away from Dell's laptops!