Sweet! I remember looking at those things in AmigaWorld and wishing I could have one.. ended up with an A590 instead with one of those nasty, slow, loud 20 meg XT drives.
I've got one of those A590 hard drive units. If you yank out the 20 MB HD, and put in a nice SCSI drive, they run excellently. I wouldn't mind trying out a IDE hack for the 500, although I think my SCSI drive runs better in my 500 than an AT drive would.
Xamiche