What can I say - I'm a meat eater. I first tried In-N-Out in San Francisco in 2004. I'm originally from the Midwest and I think I can generally say that there aren't many burgers that live up to the hype In-N-Out has.
I really like their chocolate shakes and I almost always get my burger Animal Style. My boyfriend and I have also discovered that we like the fries a lot better if we get them lightly well done.
Just as most people suggest - try something off the not so secret menu.