Understanding there's no shortage of reviews for Optimum Nutrition's Gold Standard 100% Casein, I nevertheless feel compelled to do a review as this has been a staple of mine for a while. If you don't understand the reasoning behind having casein in your daily arsenal, it basically boils down to having slow-release protein to heal and feed your muscles over an extended period of time, particularly overnight when your body isn't getting any other sustenance.
Other's have listed the profile in some depth, so I'll just focus on the highlights. 24g protein per serving, with only 1g fat and 3g carbs (and 1g sugar). One downside is the use of high fructose corn syrup, definitely a point deduction in my book.
I've tried two flavors: Cookies & Cream and Chocolate Cake Batter. Frankly, neither is that great. I actually add a couple of scoops of Quik to the Cookies & Cream in order to make it a more enjoyable evening drink. The Chocolate Cake Batter isn't much better.
No clumping or problems whatsoever.
Protein is a pretty passive supplement, and by that I mean you can't really feel its effect. But you can't argue with the cumulative effect of those 24g of protein over the course of the night in terms of healing the body and building muscle. Still, I feel compelled to deduct a point because I have other proteins that give me upwards of 29 or 30g per serving. 24g isn't bad, though.
Usually, a 4lb tub retails for around $53. That's too high in my book, but I'm pretty savvy with keeping an eye out for deals. Frankly, I know there are GNC haters out there, but this is a fairly regular red tag item for them. So, I generally end up paying closer to $40-45.