After hearing the talk that this was the closest thing to In n' Out, I headed out to Dedham last night to check it out. By coincidence, I was at In n' Out in Marin County last week, and I can tell you, it's not close.
That's not to say it's not good. The burgers were much thicker than InO, but had a nice, beefy flavor, and definitely tasted fresh. I thought they were a bit much at $3.39 for a single, and 4.49 for a double (no cheese), but the toppings were fresh and free.
The fries are nothing like InO. They're fresh cut, and good, but fairly expensive at $2.69 for a small, which I didn't find to be that big a portion, despite what I'd heard. They're medium thick, and the ones we had were fairly dark.
I did like that they have free peanuts while you're waiting.
All in all, it's OK, but it's certainly not a destination.