Anyone have opinions on which is the best and which is the worst test prep company out there?

Here’s a pretty sweet LTO ebook deal from Kaplan. You might wan to jump on.

http://www.freekaplanebooks.com/

Someone gave me a great insight on this yesterday at lunch: Ask people you survey what the actual improvement was in their GMAT as a result of the test prep company. Simple, really, but nicely measurable. Also, asking people who have taken more than one test prep course to compare them. Any other ideas?

We’re planning to do a customer satisfaction study to rank the best GMAT test prep companies. What questions would you put on our questionnaire?