The backup utility also allows you to selective wipe databases on the BB itself which is handy when troubleshooting. You can't configure or adjust sync settings without DM. It's necessary to have it running for tethering. Media Manager is in DM 4.2+ (not sure if you need it running to enable mass storage mode or not which is what I prefer). The Switch Device wizard is also in DM.

You might not need any of these. Most of our users don't have DM installed.