I wrote earlier of wanting relevancy figures. In lieu of that, how about some customer satisfaction figures? Yahoo! Gains On Google In Customer Satisfaction from Forbes covers the latest data from the University of Michigan's American Customer Satisfaction Index that puts Yahoo a hair's breath behind Google for satisfaction.
Google earned 82 out of a 100 possible satisfaction points, with Yahoo following at 80. However, Google is classified in the "search engines" category while Yahoo is classified in the "portals" category. Different questions may be involved to assess satisfaction and if so, then the scores might not be comparable.
I've looked through the ACSI site to see if the different classifications are an issue, but I've had no luck. You can check out the FAQ page and this fact sheet, as well as this commentary on the latest scores. None explain exactly what questions were asked in each category.
You can find the actual data from the ACSI here. Below is a chart that looks at scores for the various players over the past four years. Overall, Google has stayed on top but flat while competitors have generally risen, though the remain behind.Postscript: Ask Jeeves sends a note that the testing was done before it had reduced ads on its pages, something it obviously feels will lead to an increase next time.
Postscript 2: ACSI tells me "figures are comparable across categories and that the same questions are used regardless of category," so it's fair to compare satisfaction of those in the portal category to the search category. Postscript 3: ASCI also tells me that while it can't show the actual questions asked, as these are considered proprietary, this page explains more on how things are measured and this PDF file is a sample survey for the automotive industry that gives you a general sense of what's asked.