This one is gonne be a bigger feature, so it prolly will have to step back for some time, but i think it will be quite an improvement:

Since the GnutellaNet protocol doesn't support it, it will be a "local" feature.
You can search in your search results, with boolean operators, so you can sort out files with "-" if you got back too many search results.

Example:
You search for a band called "Hole" you will get a bunch of search results that got nothing to do with that band f.ex. the "black hole sun" album by soundgarden. With this new feature you can sort out all those mp3's containing "soundgarden". This will make the search result list a lot more comfortable.

PS: Add an option to quit searching when a certain number of results is hit.