I finally bought a laptop: the Gateway 200X. Yes, I realize it's not any of the four I was previously considering. I decided that, as cool as minimizing physical dimensions was, there wasn't that big of a cost in terms of weight and size to pay for a 14" screen, a nice keyboard, and a dvd/cdrom drive.
And despite my misgivings about purchasing an oh-so-uncool brand, this looks like a really good machine and has received very positive reviews. An inch thick, 4.3lbs, and at a great price-point—I configured a ha'gig of RAM, a two-score-gig hard drive, an internal 802.11g wireless card, and the extra battery for about $1700 total. The only difference between that and the XL model, as far as I can tell, is a dvd burner, a slight increase in processor speed, and $600.
Now I just had to suppress these flashbacks I've been having to junior year in high school, the last time I bought a Gateway (or, for that matter, any complete machine, as opposed to components from 50 different vendors to be lovingly hand-assembled in the basement).