Oh yes it is. I found myself on the left coast again this week and had to see if my recent revelation was true. After years of eating a standard In-N-Out Double-Double I ventured into the secret menu and I'm never going back. After a short 45 minute trip to a San Jose In-N-Out, I once again ordered the Double-Double Animal Style and found the revelation to be true. The cult favorite is a nearly perfect specimen. It's gooey, hot, and exploding with flavor thanks to the three things you will not find on the standard menu burger - sliced pickles, grilled onion, and a burger patty that has been apparently spread with mustard before it hits the griddle. Why this burger is not the standard for In-N-Out is beyond me.
The burger was so good that I was back the next day, only 20 hours later, for another. Thank God I live on the East Coast.