i use a dell inspiron 4000 with 2 battery's one in the modular bay. orinocco gold, gpsIII+ (just ordered a gpsV =) with external powered antenna. works marvelously.

here's something that's not model specific you might want to look for... some laptops don't turn the screen off when you close the lid. this will really drain your power quickly, i find that most of the power used when stumbling is used by the screen, IF it's turned on... of course, turning the screen off when the lid is closed is standard with any new laptops that aren't the bottom of the line, but a few buddies of mine have compaq's that leave the screen on so it thought it was worth mentioning.

i find that 2k works well for stumbling, just because it's typically the preferred OS for laptops in general, above 9x, that is... no comment on xp. ;-)