Avoid them like the plague, is my advice.   I made the mistake of buying an Iomega Ditto Maxparallel port tape drive, and three 7gb tapes for a total cost of about $300.  
I figured that my experiences with Iomega's Zip were good, so their tape drive must be good also.  
But alas, I don't think that I have ever encountered such a poor product as the Ditto tape drive.  
I thought that my stuff was being backed up correctly, even though I got some strange messages, that no one seemed to be able to explain.  
I found out differently when I went to recover from a scrambled C: drive.
I spent over a month trying to recover, experimenting with all kinds of combinations of settings, some working better than others,
but I never could recover everything.   And each attempt took forever, often letting the thing churn and whirl overnite.  
My 2.6gb C: drive took, at best, about 20 hours to backup, and even then, it never did backup everything correctly, even
after Iomega released a new version of their software, Ditto98.   Iomega took a lot of flak over this, and perhaps that's why
the Ditto today is sold by Tecmar Inc.
I also have an internal Ditto 3gb tape drive in my PC at work.   Same problems.  
Incredibly slow, and never could recover, and even simple recoveries of small data directories were fraught with problems.  
It's not that I'm a novice at these things, for I also had at work a 4mm DAT drive and an 8mm DAT drive, and they have worked
almost flawlessly for some time, except for an occasional tape breaking after much reuse.   But then, these 2 drives
do not use Windows software to back up with.   Remember, Windows backup software is the pits.  
But even these two DAT drives are slow, so I don't like tape drives, period.