I have a personal litmus test for new search engines - a vanity search on myself. I know my own content across the web better than anyone else's. By far, Google still rates far and above for returning the fullest and most pertinent set of results than any others. Cuil fails at this.

More generally, I compared common searches I do regularly relating to things like "javascript framework" and "css" and the results were poor.

Its not only about who has the biggest index. Its about retrieving the most relevant data from that index.

To be more crude, its not about the size of your <guess>, its about how you use it.