I've recently got one of these and have been dumping lots of old SCSI disks. With the latest firmware update this works very well, I was even able to dump some disks that had errors which caused them not to be useable as a normal disk anymore.
I'm planning to dump the real HD in my NeXTCube soon, so that I can replace it with an image on the BlueSCSIv2.
The ZuluSCSI and the RaSCSI/PiSCSI support this same functionality as well btw.