All Club Mac is doing is using a standard USB enclosure (they sell them for ~$75) and a standard IDE hard drive (20GB = less than $100). Nothing magical - it's just that the other USB hard drive makers tend to use more fancy cases, and some of them use 2.5" IDE drives instead of the cheaper 3.5" drives.
I bought a Club Mac SCSI hard drive three years ago - and it has been one of the best peripheral I have ever bought. I have never had any trouble with it at all. The Club Mac stuff is definitely very plain and simple, but it does get the job done, far cheaper I might add.
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Eliott Wolfe
Winnetka, Calif