The eee is actually upgradeable to 2GB; however, the default Xandros distribution will only make use of 1GB. Other distributions or an available modified kernel file can use the full 2G.
It is also possible and inexpensive to use a SDHC memory card as a "permanent" solid state drive upgrade. The eee supports SDHC cards in the provided slot, probably up to 256GB; which aren't available on the market yet - largest commonly available is 16GB.
I was waiting for Apple's announcement before committing one way or another; the MacBook Air convinced me to keep my MacBook Pro and add an eee for now. Maybe next year Apple will be on the bleeding edge with OLED display and WIMAX support; the Air is more of an admittedly elegant packaging job.