My first laptop was an HP Omnibook 300 or 400 or something along those lines. No screen backlight. Greyscale only. It has the cool pop-out mouse, and they somehow smashed Win3.1 into a PCMCIA read-only memory card that it could boot from. I then bought a 200MB or thereabouts PCMCIA type 3 card. This was enough for me to run Quicken and a terminal emulator. It was small, tough, and a great laptop. After that, I had the same Omnibook 600-series. Color screen. Real hard drive. Ran Win95 and friends. I added in some kind of cheesy Ethernet card and that machine got me all the way through graduate school. The only major screwup was that the VGA output tried to auto-detect if you had a projector, which didn't work with about half of the projectors at the time. Otherwise, a fine machine.
Once I finished grad school, it was on to the Sony Vaio 505G or GX. Basically, Sony's first and still amazing subnotebook. The only stupidity was the big ugly dongle you needed to get VGA output. That eventually crapped out and I got the Omnibook 500 and later 510 after the 500 had self-destructed enough times. In many respects, the Omnibook 500-series really got things right. Nice rubberized pads for your hands. No sharp corners. Very clever design, just dumb, crapola device driver support, and now lost in the HP/Compaq merger.
I definitely want to hear how that Dell X1 works out. I'm not buying tomorrow or anything, but if I did, I'd be leaning toward the ThinkPad X41 Tablet. The tablet functionality, at no extra weight, seems worth getting to play with.
Amusing footnote: shortly after I got to Rice, I went along on a research pitch to Dell (hitting them up for money to support our work). They never gave us any money, but they were remarking at my Sony 505. "Don't you need a CD?" "Naah, I've got all that back in the office." At the time, the lightest Dell laptop was stil in the 6-7 pound range. A few years later, they finally caved and started offering subnotebooks.