Full Disclosure: I've never been to Philly and am not qualified to speak about "authentic" Philly Cheesesteaks.
Today's cart, Steak Your Claim, wasn't a great Cheesesteak. I hear Cheese Wiz is how they're "really" made in PA. If that's the case then I doubt I'd like any authentic cheesesteaks.
The guy working at the cart (the owner?) was really nice and answered my questions. He also recommended their chili, which I'll have to try next time.
Overall, it didn't do anything for me. Worth another try though.