I prefer the current forum layout for reasons already mentioned and forum management is outstanding in my opinion.

However, maybe it is possible to accommodate both points:

I really like the "News Watch" and "Forum Watch" lists on the main page, often stumbling upon an interesting thread I would never have looked at otherwise because I do not have a habit of checking all the new posts in the different forums and subforums "manually". However, usually there are more than 5 new posts per day, so I tend to miss some of the updated threads.

If these lists could be extended to list all the threads updated during the previous day, or maybe even week — in essence quite similar to a merged forum but (possibly) time limited and linking to threads on existing boards — this might do the trick.