There are a bunch of features that I haven't mentioned yet that many people will find extremely helpful. I don't much use them, but that doesn't imply that they aren't good. You can archive multiple Sources in the same Archive, or a single Source to multiple Archives, or best of all, multiple Sources to multiple Archives. You'd better have wads of storage space if you want to do that. If you can create a Browser, you can print a file list, which I like doing when files are archived off of a hard disk. That way, anyone can flip through the list at their leisure to find what file they want back even though they haven't used it in years. Of course, you can search for files within archives, so you don't have to rely on the printout, but it's often easier for non-technical people to search manually. You can use the Fast Add Disks command to add the contents of a bunch of floppies to an archive, which would allow you to archive all those floppies you've accumulated over the years to a tape drive, and once you've got a file in an archive, you can copy it to another one.
If you're really paranoid, you can password protect and encrypt an archive, but I don't recommend doing that. It's all too easy to forget a password or have messy internal politics that result in a disgruntled employee changing the password before quitting. In addition, encryption significantly slows down the archiving process. You don't have to worry about encryption making it harder to recover files with a disk editor, because the normal compression (which you should use unless you've got those wads of storage space) will render the files unreadable to most unsavory people.
If you have a tape drive or other backup device that can't mount on the Desktop, you can use Retrospect's Peripheral Device Management features to Format, Erase, Retension, and Eject those devices. You can also define Subvolumes, which are really folders on a normal volume but which Retrospect will then treat as though they were real disks. It can be handy on occasion if you don't want to mess with most of a disk, but you do want to back up a single folder. Of course, a Selector could arrange that too, but Subvolumes work equally well. Subvolumes are also useful when you retrieve files, since you might want to recreate a hard disk on another hard disk without erasing the contents of the destination. Defining a Subvolume on the Destination disk will make that possible. If you have network software that mounts a remote disk on your desktop, you can backup that disk just like any other one over the network. If you don't use System 7 or TOPS or DataClub, you'll have to use Retrospect Remote to backup remote Macs. More on that in a bit.
Finally, you can do some good stuff with Retrospect's Preferences. You can turn off some of the safety alerts to speed up the archiving process. If you run Retrospect under MultiFinder in System 6, you can have it pause until you bring it to the foreground. Retrospect likes a lot of CPU time, so use this if you are doing serious work in the foreground at the same time. Retrospect will automatically format disks for you as a default, but if you're leery of that (I wouldn't be unless you have 1.4 MB disks with an 800K drive) you can shut it off. If you are using the auto-execute features in Retrospect, you can specify if Retrospect should quit when it's done, shut down the Mac, or stay in Retrospect. You should also set it to avoid stopping on errors if you use the program in unattended mode, because any dialogs will halt execution unless that option is checked. Retrospect keeps track of what it does in a Log, so you can still see easily if there are any errors. Finally, if you have a SCSI device that you want Retrospect to ignore, you can set it to ignore any SCSI number in the Preferences dialog as well. There, all of these preferences ought to keep you happy for a while.