I used my Asus eee 1000HA as my first foray into the Linux world and chose to do so with Ubuntu 8.10 Intrepid Ibex. Out of the box, my wifi did NOT work, but it was a single download and 4 typed commands away using ath5k drivers available for free online. My ONLY ISSUE with Ubuntu is the screen size of the eee screen. I do like the default 2x bars on the screen, one at the top and one at the bottom. The vertical size of the screen does make it very hard to click some of the buttons at the bottom of dialogue boxes. This is easily fixed by adding hide arrows to the panels so you can shove them off the screen when they're not needed. You can hide the bars if you want as well, so that's also an option.
Except for the wifi, EVERYTHING so far has worked straight out of the box. I reformatted the second partition as Ext3 and copied some of my MP3 collection to it. With the proper drivers, you can access your Ext3 partitions and drives from Windows if needed. Ubuntu will read the windows partition automatically, so you don't even need that.
In my opinion, slapping Ubuntu on it was the best thing I could have ever done with it... It's SO much more responsive than Windows was.