To be fair, I wouldn't use a ThinkPad except with Linux (using SUSE right now). Thankfully, many Linux developers are big Thinkpad fans, so any 'classic' Thinkpad (basically the T, W and X series), even the new generations will generally work flawlessly (or close to it) with Linux.

Really I think the only thing that might sway me is Dell's new-found love for Linux.