We are using TSM in a very large scale VMware enviroment.
With TSM you have 2 options, either cluster backup where you use vcenter and backup all VMs in a cluster. The second option is the agent backup.
Due to the scale of our virtualized enviroment as well as the amount of hosts as networks, we used both depending on the need. This however resulted in the need for a load of TSM proxies working within the virtualized enviroment, and those where resource hogs.
Managing TSM is a nightmare, and after 5 years with TSM we are doing an enterprise wide tender to find a new solution, as long as it is NOT TSM. We have looked into several other solutions and almost all are better when we evaluate from the standpoint of our own experiences and not from the brochures. So if you are going to deploy TSM i wish you all the luck and hope you have time enough for administrating it. Another thing worth mentioning is that in our large scale enviroment TSM backup is the #1 problem when it comes to VM stability, and its need for constant monitoring of vmware tools on the VMs as well as always having to make sure we do not try to backup appliances with "third party" vmware tools.