Full backup - FIVE AND A HALF HOURS LONG
It's nice to drop a tape into the drive, hit "Start" and walk away - but for 5 hours and 30-odd minutes (full system backup)? I can't use my computer during that time (both because that causes errors in the backup, and because it's a Microsoft OS, so the system is already unstable).
I'm seriously considering a DVD-R?? drive. As long as I can re-use the same media for the full backups, the cost and time make a difference.