OK, I got my 8GB A90 A04 today. Charged it up. Booted and poke around Ubuntu 8.04. Blew away the install and installed Ubuntu 9.04. Poked around a bit. Installed all the upgrades. Everything seemed to work fine.
Installed SL using a retail SL disk and the NetBookInstaller method. Hacked the installation distribution file to get it to fit on the 8GB SSD
using the method described by Mechdrew. Installed fine but failed on initial reboot with an "Operating System not found". Didn't see an obvious problem so tried it again using an 10.5 retail disk. Same problem.
Reinstalled Ubuntu 9.04 and it boots fine.
It would appear that the OS X installer isn't updating something related to the boot process. Any suggestions?
Update: Installed Windows 7RC w/o any problem. Reboots and works fine.
Update: Used 0.8.3RC1 with SL and 0.8.2 with Leopard. Tried both MBR and GUID.