Our 2+ year old Inspiron 9300s are still going (very!) strong here. Wonderful machines, though a bit large for airports and the like. The Latitude X1 (2.5 lbs) serves rather nicely for extended travel, though!

We also now have an Inspiron 9400 with a Core2 duo CPU and other, lesser differences.

All of the machines, except for the X1, have 2GB (2 x 1GB, dual-channel) of DDR2 in them. Just last night, though, I picked up a cheapish 2GB stick of DDR2 to play with. None of these notebooks claim compatibility with 2GB sticks, but that doesn't mean it won't work.

It works in the X1, giving a 2GB total there (rather than the 2.2GB I expected, with the 256MB it has soldered onto the mainboard), and it also works in the 9400 alongside one of the 1GB sticks, for a total of 3GB. The BIOS appears to have left dual-channel access enabled, despite the mismatch in sizes, speeds, and brands of sticks. So it's all nice and fast there, too.

Gotta try it in the 9300 next, just for the sake of completeness.
EDIT: Just tried it, and the BIOS only recognized the first 1GB of the 2GB stick.

-ml