To the letter
Just be sure to follow DC TO THE LETTER, or you'll be disappointed. The stretching, the extra cardio, no carbs in the evening, EVERYTHING. Those that are able to follow his instructions exactly get great results. But if you only do it half-ass or even 90%, you won't get good results at all.
If you go on his site, his forum, you'll see examples of "to the letter" devotees who look amazing. BUT you'll see many, many others who think they are following DC right, but don't look very good at all, just big and bulky.
This is my opinion from 6 months experience with it. I think I did about 90% of what I was suppose to. I gained a lot of weight and strength, but didn't like the way I started looking (like a fat moose) and got so I wasn't enjoying my workouts and never getting a pump. And when I'd flex, after several months of DC, I couldn't flex "hard" if you know what I mean. I could squeeze a muscle hard, but it wasn't rock hard, like before DC. I have a theory on this that I recently posted in another thread with the title "Am I Doing Something Wrong" or something similar to that.