TSM server was a Win2k with TSM 4.1.1 (at the time) restoring to a Win2k
Server.  Gig network cards on both sides.  STK 9840FC tape drives.  Client
was collocated by client running TSM 4.1.2.  I ran 3 concurrent restores
starting them about 30 min. apart from each other so that each session would
hopefully not be waiting on the same tape that other session was using (for
the most part this worked but there were a couple of times that a session
had to wait for the tape).

In your case, I have seen slow response from a unix client to a W2k server,
just like our previous Backup software was Unix based and I saw the slow
response from a Unix server to a W2k client.  There are some documented
changes for the Unix client that we applied to speed things up some, but
again my case was W2k to W2k.  I think that you would look at it along the
lines of Richards post in that a lot of it is in the planning.  I had the
9840's, the disk to create large storage pools and installed W2k Servers
(since the majority of our clients are Intel based machines) that had the
horsepower to drive things.  Like just about every application/environments,
if you through the hardware at it it will work.  Alot of post have been made
about AS/400 backups/restores but I can tell you I have 1 AS/400 with a GB
card that backs up 15GB in 45 min and another that has a 100MB card and
older processor in it and backups up at 15GB in 5 hours.