I love mine, it has a 1.3Ghz pentium M, centrino wireless, 30g hard drive(4200 rpm), 32MB M9 graphics, and sxga+ screen. I use the machine mainly for programming and school work. The sxga+ (1400x1050) screen is great, some might say the text is a little small, but they're probably blind. It only weighs about 5lb, so it's not hard to carry back and forth from class every day. I don't have much to say about windows, other than the default setting likes to use dynamic cpu scaling, even when plugged in. Also, the 2 games I have on there (ut2003 and gta:vc) both run fine. Performance is sub-desktop, but playable at 1024x768. I use linux most of the time, and aside from having to patch my kernel to support the alps touchpad (just to enable edge scrolling, otherwise is works as a standard ps/2 device), it was very easy to set up. I'm using linuxant driverloader for the wireless, but will switch to native intel drivers as soon as they are done.
Build Quality: Here's the downside with this laptop. I used to have a vpr matrix 180b5 that was stolen, and the cheapo best-buy brand beat out the dell in materials and build. The inspiron has a plastic lid, and the back is pretty thin (vpr was magnesium). If you press on it with the display on, you can see is "bubble" under the pressure. If you adjust the screen angle by using the top edge, there is no problem. The rest of the case is plastic, but that is not as vital as the screen back imho. With that said, I've carried this laptop in my backpack, and haven't had any problems with it being bashed with textbooks. So the lid is tougher than it lets on. The battery wiggles in its socked a little, but this seems normal (and only by a very small fraction of an inch) and is in no danger of falling out. The power button is really stiff, and feels broken (it's not).
PROS: size & weight
screen
performance
battery life (I've never run out, but I don't use the battery all that much)
plays nicely with linux
CONS:
plastic screen back
really stiff power button
BTW, the dell came with a full manual, which describes how to go about ugprading ram, hard drive, and mini-pci in this laptop.