You probably never notice the large number that appears in tiny type at the bottom of the Google home page, but I do. It's a measure of how many pages we have in our index and gives an indication of how broadly we search to find the information you're looking for. Today that number nearly doubled to more than 8 billion pages. That made me smile.
Comprehensiveness is not the only important factor in evaluating a search engine, but it's invaluable for queries that only return a few results. For example, now when I search for friends who previously generated only a handful of results, I see double that number. These are not just copies of the same pages, but truly diverse results that give more information. The same is true for obscure topics, where you're now significantly more likely to find relevant and diverse information about the subjects. You may also notice that the result counts for broader queries (with thousands or millions of results) have gone up substantially. However, as with any search engine, these are estimates, and the real benefit lies with the queries that generate fewer results.