I was wondering if there was some way to make 'Next Topic' smarter when it reaches the end of topics. In the general case where it's not a search I think instead of showing the no more topics page it'd be useful to either return to the list of topics in the forum, or even one level up from that (list of forums in the geneal case). Which is a matter of preference I'd think.
The system won't know if there are more topics until the link is actually clicked, since new topics can be added while the page is viewed. Now, it could be done quite easily with AJAX to keep the link properly updated, which would be neat.
That does account for topics being added while viewing. OTOH you could just disable the link (or better, retarget it to the index if in normal reading mode) if it's the last thread when the page was generated. I'd rather not have to bump into the end every time on the chance that there's a new topic started and would rather end up at the index where I'd see the new topic.