I administer ADSM for our site.  We backup 4 RS6000's and 5 NT servers. 
ADSM only takes up about 1 or 2 hours of my time each day.  On a bad day,
maybe 4 hours, but that is rare.  We do not backup any workstations, they
are considered expendable, all important workstation info is stored on the
NT servers.  If workstations were involved, I'm sure my time on ADSM  would
be much greater.  Our server is on one of the RS6000's, and shell scripting
a lot of routine stuff can save a lot of time in the long run.