Dymatize is about comparable to Optimum Nutrition. The Chocolate and Vanilla flavours are quite nice but the berry flavour tastes kind of sickly. It is a blend of Whey Isolate with Whey Concentrate, meaning it is slightly higher carb/fat than a pure isolate, but really, the only difference it makes is to your wallet. It is a well known brand, which means a lot considering how many brands are found under delivering on protein content nowadays.
Use it to reach your daily protein goals, doesn't matter when (pre-intra-post, etc).