I just drink MTN Ops ammo and don't add anything else in, but I will say that I don't really use it as a meal replacement, its more like a snack replacement for me.
I usually have one serving with water right when I wake up, then another post workout in water only. Then I always have a full breakfast, lunch, and dinner, and usually another snack sprinkled in there somewhere.
A serving of ammo is 140 calories, so its pretty light in that department, but it will keep you surprisingly full for a while. If I had to use it as a meal replacement, I wouldn't hesitate to do so.