Actually not only on this forum but generally in SmarterTrack product. Big difference in my case would make partial/wildcard search and language invariant search (for example many users don't use national characters when searching for something.
Example: word password in polish is hasło but many users search for haslo and in this situation SmarterTrack is not returning any results containing word "hasło".
Thread here:
http://portal.smartertools.com/community/a660/language-invariant-and-partial-search-in-smartertrack-knowledge-base.aspx
IMHO there is another thing which should be altered and it is search form on main page which returns only 5 results without informing user that there is more available in knowledge base:
Thread here:
http://portal.smartertools.com/community/a284/search-on-portal-home-page-doesnt-show-all-results.aspx