As Brett says, QuickKeys can do a good job of automating an incremental
backup.  I use that now and it's a thing of beauty.  Rather than run the
backup at startup, I run it at shutdown.  I have the QuickKeys macro set
so that it will run the incremental and shutdown the computer after the
backup completes.  Also, as Brett suggests, I have my preferences file
set so that the appropriate disks are selected (the DOMAIN statement).
I also use a trace file with trace flags AUDIT so I can review the
backup the next morning.

I also use QuickKeys to backup our Macintosh servers automatically each
night at 2:00am.  (We are still using WDSF for our main system, so I
can't use the scheduler quite yet.)

P.S.  QuickKeys timer option allows you to set a macro so that it starts
      N seconds after you start your Macintosh.  So you could run the
      backup at startup time rather than at shutdown.

Ken Rosenberry                    Internet:  hkr AT psuvm.psu DOT edu
Lead Systems Programmer           BITNET:    hkr@psuvm
Pennsylvania State University     APPLELINK: ROSENBERRY