Personally, I like the way the Galaxy Tab handles the external slot. It uses the 16 gigs of internal flash as the SD card, and the external care gets mounted as a subdirectory. Hopefully, MOTO or Google will do something along those lines.
Have you browsed the file system? It appears to me that the Xoom may handle things this way as well
I have. I currently have a 16GB card installed, but there doesn't seem to be any way to access it. No extra folders show up anywhere when I plug it in, and I am not sure what the device name would be - so even if I had a terminal installed, I wouldn't know how to mount it. If you can give some suggestions there, I'll check it out.