Some more info:
There are three new LaunchDaemons having to do with Time Machine if you look. One of these is set to automatically backup every hour on the hour, and I assume this is what is controlled by the "Back Up Automatically" option. However (from what I can see) it does nothing if your BUD is not attached. Normally backupd will log multiple messages to the console as it works, but if the BUD is not attached it seems to do absolutely nothing. No warning message to Console or anything. While at first this seems to be a deal-breaker for laptop users who are constantly on the go, the lack of Console messages to me seems to indicate an incomplete feature...as if the case that handles no BUD present isn't yet in the available builds of Leopard. Of course, that's just speculation; as it stands, Time Machine does nothing if your BUD is not attached.
Ok, then we look at the second LaunchDaemon. launchd was modified earlier this year to support a 'StartOnMount' property that this daemon uses. Apparently it is supposed to start some special backup task when an external drive (hardware, network, or otherwise) is mounted. However, again, it doesn't yet do anything. As before, this seems to indicate to me that there's still many changes/improvements coming to the way Time Machine works because I doubt Apple's engineers would just randomly add a LaunchDaemon that does absolutely nothing. This could possibly be the way Time Machine knows when to push a yet-to-be-added temporary HD backup to your BUD, or something completely different.
I have no idea what the third LaunchDaemon does. Could be incomplete, I dunno. Seems to do nothing because its set to never run.
I know supposedly Time Machine is supposed to combine those hourly backups into a single daily backup at the end of the day, but I don't see where this is happening unless it isn't added yet (which is certainly possible). Seems a bit annoying to have tons and tons of hourly backups (for non-mobile people, at least) taking up space for months back in time, though, so hopefully this will change.