I've got an Eee pc 901 running on XP. I really love it actually. The only problem with the XP version is the small hard disk, which is only 12GB, which can be easily fixed by either using a 16gb or 32GB SD card in the card reader and just leave it there, or just buy an external hard drive. The problem with external hard drive is the drain the batteries due to moving parts. And that's the beauty with these little machines. Since they use solid state hard drives, I can use it for 6 hours solid with internet on before it runs out of battery. I could stretch it to 8 hours if i had it in low consumption and wireless and bluetooth disabled.
If you are getting one, get the 901 or newer version, since the difference is really pronounced, what with the new Intel Atom processor instead of the Celeron (which gave roughly 3 hours battery life). Plus you have the ability to upgrade if you want. On the previous models the memory is soldered on the motherboard, where on the 901 it just takes 5 minutes to install a 2GB RAM to replace the 1GB that cames with, or install a new SDHC, which are a bit expensive mind you, that's why I opted for the SD card.
The keyboard is quite small, but I find it rather easy typing, even though I do have large fingers. It just needs some getting used to.
Overall, I'm quite happy with it, it's a joy to have it with you while on the train, and it does whatever a normal laptop would do (except reading or writing DVDs, which an external DVD writer would solve the problem, even though I never felt the need to buy one)