I bought an ASUS EEE 901 a few weeks ago, the 20GB Linux version (16GB + 4GB, really). The default Linux installation, Xandros, is buggy and very tinker-toy; the first thing I did was install ArchLinux on it. I also bumped up the memory to 2GB, and bought an 8GB SDHC card for it.
The battery life is impressive, I'm getting around 5 to 6 hours out of it, with normal use. You can underclock the CPU pretty easily to boost battery a bit (not much) more, and turning off WiFi buys you even more time. I've been able to watch movies, listen to music, browse the web, without any noticeable lags or speed problems.
The keyboard is tiny, and takes some getting used to. The mousepad buttons are also very stiff, to the point of being almost unusable (but you can tap on the mousepad).
The default Ralink wireless driver for Linux is moderately broken; one of the first tasks most Linux users do is get the patched version of the driver. There's source code available to compile the driver yourself, or a compiled version available for most Linux distros (Ubuntu, ArchLinux, Debian, Gentoo, etc.)
The Pico I ordered should arrive any day now, I think it will be a good match for it.