I am on digest service, so forgive me if this posting duplicates one
already placed by someone else.  Before the digression about media
prices, the question posed was about reliability.  Although HP's numbers
seem to indicate a longer MTBF for the DDS3 drives, I believe the real
issue for most of us is the reliability of the media and their contents.
Anyone who has suffered an unreadable backup knows that it ranks
right up there with the heartbreak of psoriasis.  (For younger readers,
this is an allusion to a television commercial that annoyed everyone back
in the 60's).  Because of DLT's linear format (no helical scan mechanism
to get out of alignment), and robust error-correction schemes, the error
rate on DLT media is breathtakingly small.  If the drives need service a bit
more frequently, I'm willing to pay that price for reliable backups.