Having soldered an IDE connector to the circuit board my brief experience here is:
As the 200EM will only boot from hard disk this means that you'll have to find another system to perform the install on. With the grub boot loader certain information is embedded into grub as part of its install process. This means that your hard drive MUST be /dev/hda when you do the install as it will be definitely be /dev/hda when you come to boot from it on the 200EM.
I got burnt by this at one point when I took the easier route of just connecting the installation hard disk to the IDE1 interface of another system and consequently the did the install to /dev/hdc. You cannot subsequently manually edit/re-install grub so that it will work when the drive becomes /dev/hda. I had to dismantle my system a little further and connect the installation drive as /dev/hda and repeat the installation.
At the time of writing [January 2010], as part of another project, I have Tinycore 2.7 installed on a hard disk. I connected this to the IDE connector and booted and ran it - sort of successfully. This version of Tinycore runs happily on another Geode GX1/CS5530A based hardware, but on this hardware the display is rather strange.
The desktop of a Tinycore system should look as shown on the left. With the RWT200EM it appears as shown on the right. The system is obviously working with 1024 x 768 screen but the display controller looks like its been set up to show a 640 x 480(?) window of the top-left section of the underlying screen.
Having recently [August 2010] been trying out DSL 4.4.9 I revisited the Relisys to see if there was any difference in the way the display behaves....answer is no. What ever display resolution I pick - I tried up to 1280x1024 - the monitor always shows a 640 x 480 window of the top left section of the underlying larger screen.