It's long overdue that analytics packages diagnose the quality of site search and Google announced several additions coming soon to Google Analytics at EMetrics. While GA is late to the game with on site search query term analysis, they are adding some diagnostics for user success with search.
As a partial solution, I historically have set up a funnel mapping search result to clickthrough success by adding custom urchinTracker results to all search results pages and pages referred by search results. Here's what the various views looks like:
Search success is a tough thing to measure. Search, then click is a clear success pattern, but what about search, refine, and then click? What if users click several times?
Check out Avi's post for screenshots of the new reports and my post in the webanalytics forum for some of the wider issues.
Additional features are coming for more detailed event logging, including default outbound link tracking, but the details are not yet available.