After my current experiences running linux on a laptop with an optimus enabled graphics card I can safely say that I am never again going to buy a laptop with discrete graphics to run linux. It's been a pain getting Bumblebee to work (optimus drivers), and even with it working certain parts of the hardware are still closed off, thanks to limited driver support.

Not sure. I haven't seen one in the flesh, but I've heard good things about it. Nothing first, or even second hand though.

Personally, I wouldn't buy an ultrabook for the graphics performance, cooling is just too problematic to do anything overly shiny in my view, but I can't imagine you'd have issues running a shiny window manager or decoding 1080p video, which is the two most graphics intensive tasks I do.