This tool gives tons of useful information. I got the following message from Google right after using serpanalytics the first time - probably because it's accessing google too many times in a short time span:
... but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can't process your request right now.
We'll restore your access as quickly as possible, so try again soon. In the meantime, if you suspect that your computer or network has been infected, you might want to run a virus checker or spyware remover to make sure that your systems are free of viruses and other spurious software.
We apologize for the inconvenience, and hope we'll see you again on Google.