I've driven by this place many times but never tried it. The whole "cash only" thing sort of threw me as well.
Well, I have definitely been missing out! Their menu is pretty basic (but in a good way). I went with the Big One with Cheddar cheese. The burger was great! I didn't get fries this time but definitely will on my next visit. Seriously, check this place out! Oh, and they have an ATM there, FYI...