Here is an article by Aaron Wall about all the keyword research tools that they have out there. It’s pretty cool. Check it out.
“I have had over 100,000 ad displays in the last year and a half. Of about 60 keywords in that keyword group Google has sent my client traffic for about 30 of them, and 11 of them have converted to sales. One of the terms that converted to a sale was ABC, which had the lowest conversion cost, but was quickly disabled since the clickthrough rate was too low.”