Bullstorm’s Keyword Manager, a shareware iPhoto plugin, looks like a great addition to Apple’s consumer photo management application.
I’ve tried both alternatives — the built-in keywording UI, and the freeware Keyword Assistant — and neither has been entirely satisfactory. Of course, I now have those experiences to compare against the much more effortless tagging in the current Del.icio.us interface, which is one of the most fluid keywording interfaces I’ve used yet. I don’t know if Keyword Manager will be an improvement (especially one that is almost half my cost for the iLife suite), but it has promise that it could be.