Heres some answers for you:
1. Search feature: "View Posts Since Last Visit" added to forum listing
The code this this can be taken from the new Search module, which allows you to search in forums only.
2. Forums with new posts since last visit have "yellow" or "turned-on" icons in listing (this may involve adding a row of icons to the listing)
We have bold headings at the moment. I guess this wouldnt actually be a hard job!
3. Admin Option Added: "List X Forums on Each Page" to keep forum listing from splitting over multiple pages
You can already. Its either on Admin->General or on the admin->forums page. I think by default tiki is set to 10.
4. Admin Option: Allow admin to organize/order forums manually
This is a needed option!