Ubuntuforums.org might be a better place to ask than news.YC, though I'll say I'm quite pleased with my Thinkpad Z61m. It's no longer available, but I'm pretty sure the widestreen T60 has the same hardware in a much thinner, lighter package for the same price. The Macbook-sized Z61t is also a good bet. Ubuntu almost works out of the box, though I had to install a video driver before I could start X on the live CD. Debian works with no more hassle than usual.

I've never heard Thinkpads called pretty, but they do look like the serious machines they are. Dells are mostly cheap crap, and they look the part. I wouldn't worry too much about looks - instead, consider that Thinkpads, like many Apples have magnesium frames and hard drive shock protection.