Well most of the issue I have with Linux is graphics compatibility, that being said, I'd recommend any with an nVidia GPU over one with an ATI one. With that you will certainly have a much better experience.
Having said that, for window compositing the open-source radeon drivers seem to work fine as long as you don't go for a bleeding-edge chip.[1] For games, the proprietary nvidia drivers are likely better and might be worth the extra hassle (but realistically, booting into Windows is less hassle and gives a bigger choice of games... Also, realistically, you won't get a powerful 3D chip in a thin & light laptop).
[1] I've never tried the open-source nouveau drivers for nvidia chips; they have apparently been improving in leaps and bounds.
Reference?
There are Ultrabooks with discrete GPUs.
http://blogs.nvidia.com/2012/03/real-ultrabooks-have-gpus/
http://hothardware.com/News/Upcoming-Acer-Ultrabook-To-Featu...
Re the announced system: interesting - does Optimus work on Linux these days then? Last time I checked, the GPU on Optimus systems was dormant on Linux.
Optimus is not used on Linux.
I suggest Intel because of the lower power consumption.
But I think they promised OpenCL for Ivy Bridge.
Nvidia may seem better because they only have close source drivers. Compare it with catalyst, and they are pretty much the same (except you will not get dual monitor easily with Nividia)