Robert,
        We currently use an STK 9710 with 4 DLT7000 drives (as well as 2
IBM 7331's with 8mm drives).  We purchased the STK 9710 because it scales
well (up to 100 tapes and 6 drives), and because our mainframe has a bunch
of STK PowderHorn's.  When our 9710 works correctly, it works very well. 
But when it doesn't, it can be a pain.  We have been dealing with the exact
same problems that Sandye J. Jackson was describing earlier in this news
group.  As well as tapes stuck in drives, drives that think they have tapes
loaded, but don't, bad cables, bad tapes.  Some problems are to be
expected, but this library seems to have problems at least once a month. 
We use the 9710 much harder than we do our IBM 7331's, but our 2 little
7331's only fail about once for every 15 times the STK does.  Now it may be
the fault of the DLT drives, or maybe not.  But the STK does seem to be
lacking in error detection.  That is, when a hardware error occurs, it can
not always be easliy traced.  We have now ordered another library, but it
is an IBM, not STK.