I did a bit of testing with the comms-system thingy by modifying the pacificfighters profile that came with TB. Anyone interested (and who wouldn't be?) can download my test version from
http://www.student.oulu.fi/~ailomaki/tb/commstest.zip
Go to the comms-tab and start clicking. One of the problems I noticed is that the TB back-function isn't exactly like the one in a web browser, for example. If I click back in one tab and again in the next I'll end up in an endless loop instead of going back to where I was earlier. I can get around this on many occasions, but there are a few tabs that don't have properly working back-buttons.
Another issue is that it would be nice to be able to send function "comms cancel" when I exit any of the comms-group tabs, but only when I go to a tab that doesn't belong to the comms-group (I don't want to cancel comms when going from one comms-level to another). This isn't exactly a vital feature, but perhaps nice to have.