Actually, In & Out fries are OK if you get them RIGHT after they get done cooking, when they're still hot and sizzling. They get cold really fast, though, and at that point get really nasty.
I have no idea why their fries aren't that good, though. I mean, you can see how they make them: Take potato, put it into press that turns it into fry-shaped potato hunks, toss hunks into hot vat of oil, cook. Remove from oil, add salt, serve. You'd think they'd be great, since they're actually making them from scratch right there. It must be something in the cooking method, or maybe they use non-flavorful oil or something.
I suppose they need to try using the more traditional fry-cooking method and see if that helps: Cook the fries for a long period at lower heat to actually cook the potato, take it out, let it cool. Then, toss it into a vat of REALLY hot oil for a much shorter period of time, to reheat them and put a harder crispy crust around the outside.
-Arlos