If you're using Google Enterprise to fuel your search, then a new feature can help you tweak the search results you're getting. The feature is called Side-by-Side search and it's been released in Enterprise Labs.
You can use the tool for a variety of comparisons including existing search with Google Search Appliance or two different back=end Google Search Appliance settings.
With side-by-side you can test Google's enterprise search against other company's offerings. I'm guessing Google's confident enough to think they'll consistently win on the comparisons.