I'm not sure where we stand in terms of a reasonable and reliable search option for our forum, but what's currently in place does not work - or, at least, it does not work in Opera. It's been long enough that we've lived without a decent search tool and I think it's time to get it fixed. The single best search tool would be to have the integrated SMF search tool working.
I've tried the upper-right (powered by KnowledgeDex) search tool and it is working very well,
though it _mostly_ worked for a while, it does not work any more (at least not in Opera). The wheels just keep on spinning and no results are displayed. When it DID work it would provide mostly useful results but after visiting a result and going back would cause a "skip" in the process. IIRC, it was as though you had hit the back button twice, however there was no way to move forward without ending up at the forum result again. Quirky to say the least.
I've tried the SMF navigation bar search tool (Home Help Search Profile etc) and the results it brings back are poor, at best. Often times my search terms are not even found in the "most relevant" results that are shown - it takes digging through the results to find something useful. On the bright side, at least this tool gives results - knowledgedex does not. When a forum's search tool is working (phpBB or smf), it is very easy to work with. I think this would be choice #1 for me in terms of a search tool.
I've tried the google method (search terms site:forum.vectorlinux.com). This is by far the most reliable search results at the present time, but a very non-standard way of search a forum. Not many folks actually think that in order to search a forum they're currently visiting they'll need to leave the site, visit google, and enter an "advanced" search string like the aforementioned string. On the bright side, it gives reliably reasonable and relevant results. Regardless of actual forum search features working or not, this is a viable _backup_ option. It should not be the standard since many folks are not familiar with the "site:name.of.site" method of searching a website.