I haven't worked that much with TSM but I've worked quite heavily with
Netbackup, Legato and EMC EDM. Netbackup is far and above legato. Legato works
for small to medium sized environments but tends to become unstable with large
loads. 6.X had a problem restoring more than 300gb last time I used it
(november). Appliying the latest patches didn't help. There was an unexplained
problem with the indexes. Legato support had no fixes or ideas as to what might
be wrong. EDM is a convoluted nightmare and of course only really useful in an
all EMC environment. Even then netbackup's ease of use out weighs EDM
integration with a SAN environment. Plus you have to have EMC's approval do
anything other than a network backup. Netbackup isn't perfect either but I've
always found I can live with it's limitations given the other options out 
there.