SCSI2SD: Is it worth a try?

What is the experience with the SCSI2SD with old computers? It looks to be SCSI-1 and SCSI-2 compatible and I see a lot of reports of usage on this list. I am curious about how well it works and which version to get. Versions up to 5 seem to be GPLed and reasonably available. V6 does not seem to have schematics or boards open sourced and I haven't seen a supplier for them. The web page lists some sources, but they don't have the V6 available. It looks like the V6 is not open because someone used the design without following the GPL. V6 claims synchronous transfers, but I don't think most of my hardware supports it. That consists of VAXstations and qbus scsi cards. If I was after speed I wouldn't be using old hardware, but the speed has to be consistent with the era. Chuck