Common knowledge says that whey as vital post-workout to provide the body with quick access to amino acids. The debate is still up on high GI vs. low GI carbs both workout. I personally use both, I basically make oatmeal, add some sugar and whey powder. I used to think that this was a good idea, but I make the oatmeal with milk. I also use milk in all my protein shakes.
The question is, since milk protein is 80% casein isn't that slowing the digestion of the whey. Casein protein slows down the digestion of other proteins. So the 6.4 grams of casein in a cup of milk should stop the whey from quickly digesting.
Does this mean no milk post-workout? I don't know if I can ever get to the point where I would do vanilla or chocolate mixed in water (maybe those expensive, fruit flavored isolates).