An anomally with the "About this site" forum:

In the "DotNetNuke Forum" view (http://www.dotnetnuke.com/Community/Forums/tabid/795/Default.aspx) the most recent post is reported as "11/6/2009 7:03 AM
by Crispy". However, if you enter the forum (I tested as an unauthenticated user and logged in as myself) this post is nowhere to be seen. The most recent post is "12/10/2009 6:09 PM by Philip Beadle"

A few words about performance here (specifically):

• The SQL Profile results of the new forum vs the old forum are better, there is no doubt about that. 
  • DB usage is lower too (calls to it, duration, number of read/writes).
• Load testing has shown the new module overall performed pretty well (against this site). 
• There are other modules/issues/errors on this site that affect what happens here. 
• The module depends heavily on profile data, this is a long running core query when the site restarts or it was a user's profile that hasn't been loaded.
  • Remember, the way profile is stored on a site like this there are millions of rows of data to retrieve from. 
• I have yet to see a page take anywhere near 3 minutes to load. On initial DNN site startup it has historically been somewhat long to load, but we are talking about 1.5 minutes tops. 
  • I am not dismissing your claims, I just cannot verify it after trying to tax this module the past 24 hours (yes, almost all of them). 
• As for Caching:
  • No user specific data (ie. retrieved aggregated forum content, search content, available forums/groups) is cached.
  • User profile is retrieved from core once for each user, then cached at core level and the forum also caches a forum user object (that contains the profile info)
  • Forum Information, Thread Information and Group Information are cached when loaded (this is on demand, part of why the initial load does take a few)
  • Specific Posts are NOT cached. 
  • Forum configuration is stored in ModuleSettings and therefore cached at the core level.