I have two SCSI-kits, one in B1230-IV and one in B1260. Both work just fine. The speed is much better than on any IDE-hack on A1200 and transfers are done without load on the CPU (which is the most important thing when using slow 68k CPUs).
They're not rare either... our local reseller has them still in stock for example.
Only problem I had with one CD-RW drive, but it was solved by soft-upgrading the SCSI-kit's ROM. I've had lots of different devices in use: four different DAT-drives, bunch of CD-ROM/RW drives, dozen of different HDs, scanner.. at the best times I had whole SCSI-chain full. External SCSI-cases are nice too
