All great points mentioned here. Lightweight; you can get real light these days without being a DR. I love widescreen ever since I bought my new Thinkpad T61p and the poor displays on the Thinkpads are a thing of the past. I highly disagree that Thinkpads are ugly - they're made for efficiency and professionalism, not for show. Linux; my machine came with SLED of which I partitioned for my love of Ubuntu - gotta have Linux for kernel hacking and that obsessive need for ultimate control of your OS.
All that said, I'm a power user and by that I literally mean I handle my laptop ruggedly(and I'm sincerely not a klutz). For this reason I need a Thinkpad for always on the go and durable performance. They take a beating and their customer service(warranty related) is the best in the business. Had many other brands that crapped out after six to eight months on average - Thinkpads last on average three years before I call in for warranty service(high resale value). My T61p is both lightweight, high performance, widescreen, and allows up to 4 GB of RAM, rugged and goes with me everywhere while taking bumps and bruises along the way. Need a new keyboard because your hackin skillz have worn away the home row, space bar and number row? Call in a service ticket and get a keyboard shipped out and arrived to your door in less than two days(Bigtime priority).
Once you go Thinkpad, you never go back, at least for me anyways.