Yes, a week or two ago I replicated the site on a dev server and identified a couple of bottlenecks. One is mentioned on this thread:
It has to do with a scheduled proc in the notifications package which runs every minute and is a *huge* resource hog.
Creating new objects is also slow (fyi, creating a new post creates 3 objects I think). Specifically, there is a query in the "acs_objects_insert_tr" trigger which seems to take a while:
where context_id is null;
Don says he has ideas on how to improve this. However, the bigger gain would be fixing the notifications query I mentioned earlier. There may be other issues, I don't know.
I apologize to the group that I haven't made the time to work on these issues. I will try to do so this week.