I agree with you both. The reason I'd add is that it's pretty simple. FitDay is trimmed down and bare bones enough that people shouldn't have to rely on it forever to lead a healthy life. Since there are no bells and whistles, the user doesn't have to be removed from the process as with some other sites that mysteriously come up with a point value or letter grade for certain foods. FitDay rewards you for sticking with it -- once you know its quirks and how to work around some known problems, it can be pretty darn accurate. This has been shown time and time again. Sure you have to put in the work "up front" to add your custom foods and whatnot, but once you get used to it, having that kind of control within this simple platform is all you really need.
I have not tried other sites, but I *have* tried keeping track of nutrition-related things in a notebook and FitDay is better for that purpose hands down.
I personally feel that when people find major faults (beyond just preference for one site over another) with FitDay, their gripes function as a sort of excuse. Just because Fitday doesn't do absolutely everything does not mean you cannot log your foods, loose weight, and get a handle on your habits by using this site.