I got a laptop from ZaReason for work, which I use almost exclusively for ROS development. It wasn't cheap, but they were one of the few places I found that sold Linux laptops with an 8-core i7 and nVidia graphics. When I got it, it was slightly behind the cutting edge, a bit heavier and bigger than the best out there...which I guess is to be expected for a linux-specific laptop.
We've just recently gone from Ubuntu 12.04/Hydro to 14.04/Indigo. I haven't had a problem with it yet, and will likely buy from them again when the time comes (especially after watching some of my colleagues wrestle with video card driver problems on their ThinkPad and Alienware laptops).