>I am quite disappointed by the TSM software performance. ...

Have you looked at the suggestions under "Backup performance" in
 http://people.bu.edu/rbs/ADSM.QuickFacts ?
Two classic causes of performance problems are misconfigured
networking and virus protection software.  File system topology and
network loading are also substantial factors.  How long does it take
a native W2000 file system scanning utility to traverse the file
system?  (File systems with thousands of files in one directory are
A Bad Idea.)  How long does it take a client running on the TSM server
to perform a backup without networking?  Have you pursued the items
in the Performance Tuning Guide?
You have to break down the factors and examine each.
Blame TSM only if you ultimately find the sluggisness to be caused
by TSM.  But you have to do the basic systems analysis to isolate
performance factors in your mix.

   Richard Sims, BU