I've tried using SuperDuper! with my
Vantec NexStar 3 2.5" IDE enclosure. I've tried multiple drives with mostly poor results. The backup usually works. Afterward, however, Mac OS X (Tiger) sometimes refuses to mount the cloned drive; the drive never appears in Finder and nothing useful appears in the system log files.
I have never successfully booted to a drive in this enclosure. I recommend staying away.