I'll blaspheme and say that I don't think In 'n Out Burger is very good period. I remember shortly after I moved to LA some of my friends made a fairly big deal out of how I had to try In 'N Out. I expected something special and instead got an entirely mediocre burger and fries, whose main distinguishing feature was the Animal Sauce, which I found slightly disgusting.
I later tried their stuff without the sauce and it left no impression on me either way. Lots of people down here clearly love it, though, judging by the lines. There's a joint I pass by on my way to work every day and the drive-through is always backed up into the street, to the point of causing minor traffic jams.