It's a legit operation, by the same folks who do quickenloans, which is also very legit.
Yes, you have to accurately answer some questions about your credit history, which I've found to be sometimes challenging (What was my auto loan payment for a car I bought 10 years ago? Tough one!)
One thing I have just realized which I don't necessarily like is that the score they provide is NOT a FICO score. I got excited that my score was higher than I expected, but it's because it's generated by a different algorithm than a FICO score. I have yet to buy into one of their plans, I'm still not so sure paying them $15 per month is going to make it easier to raise my credit score; it seems all I need for that is to have more money and pay my bills on time!