A custom displaytype, so we can go directly to the threads
Some kind of rotation mechanism

Could you elaborate on these idea? I'm not really sure what you mean.

Newer replies should be shown first (or some easy way for us to know that there is new content)

I've put in a patch to order replies by date (newest first). Let me know if it doesn't seem to be working as expected.

I'd also like to set up some kind of notification of new posts (as I mentioned in usergroupnote devdoclet).

Update: I have made it so that when someone posts a direct reply to a group — which is essentially a top-level post under a group — it sends a message to all members of the group, something like this: There is a new comment on pmdev by jdporter...

Thank you!

A custom displaytype allows the page to support different views, e.g. for a poll, displaytype=vote takes you to the voting form. I think we'd want someting like that so we can see the usergroup threads directly (to keep the page less "busy").

A rotation/paging mechanism would ensure there are only N threads displayed at any time, however given how low participation is right now, this may not actually be a problem.

someting like that so we can see the usergroup threads directly (to keep the page less "busy")

Ok, so you're saying a view which is very much like what we have now but without the group info stuff (description + member list) at the top?