We're only using user assignments here, no machine assignments. Turns out that's a good thing because machine assignments aren't supported at all in 3.0! Don't know if that'll change down the road or not.
I've got the 3.0 OVA downloaded, but not deployed yet. Too busy trying to put v7 through its paces... if I can just get this Instant Clone functionality to work a little more smoothly (and get stacks to attach) maybe I'll be motivated to. So far I like some of the new v7 functionality, but overall I'm still mixed. VMware is still adding functions without any attention to operational details. Take the Instant Cloning, for example - no CLI support (so I can't script publishing a new image), and images aren't treated as top-level objects so you have to go into each pool to make a change. For now there are fun things to play with, but it's just not really usable/scalable. Sad 
Of the laundry list of bugs and feature requests I gave to VMware 2 years ago, which prompted in person meetings with VPs, etc, I think probably less than 10% have been implemented. Basic stuff like sort orders (session lengths), multi-select session logoff, tracking client versions - nothing!