Well, first of all, let me say that I'm not involved in the programming of the reports, the collection or interpretation of the data, or anything like that. My role is within the realm of infrastructure; I put servers on-line, maintain internal security, do domain administration, etc. The closest I get to the "real" business is that the servers which process credit cards are some of my servers and the areas for data storage are allocated by me.
Carfax's vehicle history report is, in my opinion, an incredibly useful tool. As an employee, it's something that I'm proud of and very confident in. Again, in my opinion, it represents the most accurate information that anyone can supply regarding the history of a car, and were I buying a used car, there's absolutely no way that I'd consider the car without seeing its vehicle history report - and specifically, Carfax's vehicle history report. I'd also want the safety and reliability report that Carfax provides.
That said, I'd also have an inspection done, and more specifically, by a mechanic that I trust. Not only is this something that Carfax recommends, but it's something that simply makes sense. I'd look at going with my own mechanic that I know and trust rather than one of Carfax's inspections through one of our new programs, mostly because of my own comfort with my mechanic - after all, if something goes wrong, he'll be the one fixing it, and I want him with some level of comfort and familiarity with the vehicle.
I'd never heard of a Carfax vehicle history report until I came to work at Carfax. Part of it stems from the fact that I've never purchased a used car; part of it stems from the fact that I don't know much about cars in the first place. And, to be honest, I've always been skeptical about purchasing "information" on the Internet. However, seeing what we do first-hand, seeing the meticulous nature of some of the work, and knowing the great pride that our staff takes in our data and our report, I have a great sense of pride in our products. I know I'm working for "the good guys." What I've seen has turned me into a believer. And because of that, I'd trust Carfax when they say, "Get an inspection by a mechanic."