Results from preliminary tests Edit
EXT3: recognised (interesting since this is not mentioned in official papers)
Debian: can chroot into a mipsel Debian Etch file system
The Freeagent Theater will put itself to sleep after some time and shut down USB and some other services to save power and won't respond to keyboard commands until woken up by the power button.
Possible added functions Edit
ifconfig available in busybox. Whether it will work or not is not certain until a network interface such as a USB to NIC adapter or wireless card is configured. A kernel module for it has to be compiled though. Anyone interested in mipsel cross compilation?
Since Optware is already working very well for mipsel, having working network can turn the Theater into a useful NAS thanks to its 64MB of RAM.