Snap add a suggest box when you type in your search. It work a bit better than Google Suggest because he does substring and not showing only words by the leading character you type in.
Also at the place to display the number of results, Snap display the number of searches performed by users, like the Overture tool who sometimes give you really bad measurement influenced by their own PPC campaigns.
With WordTracker, the Snap Suggest give us a third source to see how a word is popular in search. The drawback is it's not working with foreign language when you got diacritic in the character.