What VMSes Support Full Multicasting?

As few as possible, I hope.  It's a terrible technology.    It presumes switches will manage the traffic, it's not secure, it does not provide end-to-end assurance the data got there, it provides no flow control.  (And it's easier to code than a real tcp stack so it's a sign the implementation is weak.)

Genetec Security Center supports multicast well, and from many different brands of end devices.

In my experience (as a systems design engineer at a distributor) it has clear benefits when trying to achieve high camera densities with multiple viewing clients or redundant recording requirements.

Dallmeier products are multicast compatible...

You can multicast from the camera, or out of the recorder. If you really want you can also multicast record into the recorders as well.
Both of their VMS products, Semsy and Smavia will also work with multicast, but Semsy will actually manage the multicast streams and turn them on / off when the MC streams are required or not.

Disclaimer, I work for the Australian Dallmeier distributor in a technical / sales role.

Just out of curiousity - why do you want to have multicast?  

it is must "by regulation"  in my area to have multicast