I'm not someone who enjoys much drinking the milk left after cereal, so I usually use just enough to get the cereal moist enough. Unless, of course, the cereal's chocolate, in which case I have every intention of drinking it and dump as much milk as I can into the bowl. Sometimes cereals do need that extra glass of milk on the side if it's a cereal that withstands moisture (Cap'n Crunch for me, usually) or if you get a cereal that has a taste rich enough.
I'm on the other side since I can't really eat oranges or drink their juice and milk that close to each other without getting sick. Ditto apple juice. I personally only drink juice if I'm having something more savory, say even a bagel, or sometimes pancakes.
I've also noticed that they've backed off on saying "complete breakfast" and say "good breakfast." A big breakfast full of protein is better for you than cereal, though frankly I can't handle a big breakfast most of the time (weak morning stomach), and a light cereal breakfast, sometimes with toast or small breakfast pastry, is what I prefer.