What do you think is the best overall PPC search engine, taking into account things like ROI, traffic generated, traffic quality, click-through-rate, conversion rate, etc.

The candidates in alphabetical order: Brainfox, Enhance, ePilot, Espotting, FindWhat, goClick, Google, Kanoodle, Mirago, MyGeek, Overture, Search123, SearchFeed, Turbo10, Xuppa.

What is your opinion?