In our classified forums where we have For Sale, For Trade and Wanted ads, members could quickly filter the ad types.
And the same for general forums with Review, News and Article threads which get lost amongst the other threads.
Obviously the thread prefix filter functionality exists, but we feel it's a bit hidden at the moment.
If there were a number of tabs above the thread list, which only appear when there are prefixes, e.g.
All threads | For Sale | For Trade | Wanted
Then it would be immediately obvious to readers what the tabs do, and would make the whole experience of finding the ones they want much easier.
Maybe we could load the thread list filters with an Ajax call?