That said, if I had to buy a Linux laptop, I'd go for a Lenovo ThinkPad, but I'd make sure the one I bought had good driver support. Since the ThinkPads were introduced, I've only ever heard two things about running Linux on them -- "I can't find the @#$% driver for the @#$% @#$%," and "it runs beautifully."
Lots of time gets sunk into getting and keeping all of the features (that you'll end up wanting) running on Linux boxes.
I did Thinkpads for as long as they've been around and fought that fight over and over and over again. Then I finally switched my laptops (and only my laptops :-) to Apple Powerbooks. Fully outfitted it was basically the same price as the high-end Thinkpads.