Bob,
I have Gcode running off of an SD card on the Sanguino. I am working on cleaning it up and getting my machine back up and running. (This is after changing from the PIC electronics to the Sanguino)
I have a LCD board but I have not yet started on the code to integrate it as of right now the firmware will read the first file on the SD card and will display info over the serial port.
We are using the Sanguino Motherboard which is not released yet from the RRRF.
So to answer your question then yes this would make a Reprap 99% operational if not 100%.
The plan is to possibly be ale to run the 3rd gen electronics this way also which would improve things even more.
Bruce Wattendorf