I like the Designer stuff. It's not quite as tasty, but is reasonably priced and is an easy way to add extra protein. I still prefer food, tho. Supposed to increase strength, maybe energy, by allowing quick replenishment of ATP stores in muscle tissue. Also adds size via increased fluid retention in muscle tissue.
Latest word is that caffeine negates the strength increase.
Bargains can be found, especially if you buy in larger quantities. Supposed to mimic to some degree the action of insulin in moving nutrients into body tissues. They say it's toxic and some recommend cycling 6 weeks on and 6 weeks off. I tried it for six weeks and didn't notice any effect one way or the other. I actually think you'll notice the action of this supplement on a reduced carb diet.