This was all just a test. While the feature is fairly streamlined, it is too resource intensive. It has to do 2 separate resource intensive jobs (load active list, find first/last msgs, and then find the current forum next/last msg). That's a bit too much to work with at current load levels.
However, I do have a long term hack in mind that will work a bit better. It's on the back burner though as a future upgrade.