I'll think the best way to improve searches is to search threads and sort the by relevance (ammount of matching posts in a thread / total posts in the thread). And, if it's a recursive query (like in the example) show announcements and sticky threads at the top of the results list. The secondary sort method would be relevance (as said before) and the tertiary (or w/e) the date/time.
Searching "sponsor" would return:
1.
http://shoutbox.menthix.net/showthread.php?tid=17940
2. [any sticky about sponsor program]
3. Descending importance,
I'd suggest to add this support-search by default and make it possible to switch back to default DESC-Date search.
Just an idea... again