@Floid:
This sounds interesting. According the docs you supplied, it is on the SCSI-level implemented as a standard
SCSI communications device and should atleast be acting correctly. The docs you supplied was well speced so the biggest problem would probably be to find someone to write a nice serial device for it.
Regarding the speed - 57600 is plenty enough for it to be useful. I also saw the Sx-1600 model which was supposed to have "high performance serial ports" and should thus be able to to even higher than the 57600 of the ST-1800 as its serial ports was just denoted as "serial ports".
/Patrik