Hmm. I just tried it out to see what they would recommend for me. I love jeans, wear them everyday, and feel pretty educated on how each designer fits on me and in general. They recommended William Rast, which I have tried and thought were so-so. They also recommended Hudson, which I know fit amazing on me, so they definitely hit the nail on the head with that one. They did not recommend True Religions, which happen to be the best fitting jeans I have ever worn. I wear them almost everday. They also chose 7FAMK and Paige, which are absolutely terrible on me.
So, from all that garble I just wrote, I would conclude that it is a great place to start, but I would definitely go to a department store or jean bar and try on as many styles and brands as you can with the help of a store associate.