Hmmmm, I was surprised to see my post count drop under the new system given my post-2002 join date. Not a big deal, just interesting. Might it be due to comments in the photo gallery not carrying over? EDIT: Oh, nevermind. Having re-read your post, Wayne, I see there are multiple data issues involved.
Can I suggest making the Latest Posts module on the righthand side into a Latest Active Threads module? It seems a little redundant to have multiple posts within the same thread using up slots. And is it possible to keep the sidebars within a thread like we have now?
IBrowse seems able to handle the basic functionality, so hooray.
Out of curiosity, how does the new system compute "active members"?
I'll hold off on other comments until things are more finalized.