It looks nice and polished but I can do this for free at http://i.seemikecode.com/

At the very least, I'd make a true free plan and let your customers try before they buy. I'm not interested in a tour, I want to actually use the application before I sign up.

I like how you store the test results on your end. I don't think I'd ever use that (because we don't really care about previous tests of rejected candidates) but it's a nice touch.