I found and fixed the bottleneck that caused the search results to take forever to display. I guess the icon creation code is fast enough for the slow find routine used by gnome-search-tool. It is painfully slow, taking 30 seconds to display a 1,000 file match, even though the list took 2 seconds to lookup.
I see Nat listed Medusa among the promising new features for GNOME. Wow. I wish I could work on metadata full time. I don't own the Medusa project, I'm not even the maintainer. Anyone who would like to contribute is welcome. Nat also mentioned Storage and Dashboard with the hot ideas, and I'm also interested in them. Some collaboration between all projects would really transform GNOME from a smart desktop to outright brilliant.