stevec
For the PT page about VCAs, there seem to be some fine points about grouping VCAs, how sends are handled, and how faders react when hitting the bottom of their travel, but without going through SONAR and trying those things using groups I have no idea whether they'd would react the same in the end... just under a different name. There's a lot to absorb.
For temp groups, yeah, SONAR does something similar by selecting multiple widgets and then Ctrl+dragging - works great (and for just about every widget type).
Just checked out track stacks in Logic - you get the VCA/lead fader, the desired behaviour when faders hit top or bottom (they "remember" their relative position once you move them back).
As an added benefit is that it also works as a folder track in the arrange/track view.
I can see how this can be useful, as you have one extra level control. Incidentally, the lead fader can also be quick linked to the tracks in the group.
The one thing I still have to figure out is the Send paradigm.