I have just finished a big tub of 'Instant Whey Protein'. I was taking two to four scoops per day - two with my porridge at breakfast, and two in a water based shake after strength training workouts. It is rather expensive, and with Christmas around the corner, I can't really afford to buy a new one.
Was it worth it? I don't really know. Like all supplements (its the only dietary supplement that I have used), there is an element of psychology going on. Whey is a protein-rich dairy product. The usual advice for strength training nutrition is to consume extra protein, and to consume protein throughout the day, usually along with carbs. However, health professionals do warn us (I don't have a link, try searching for it), that too much protein can be harmful.
I'm sure that you already know this, but good proteins can be found in chicken white meat, turkey white meat, tuna, eggs, salmon, white fish, lean red meats, dairy products (cottage cheese is a particularly good source - just make sure that its made from skimmed/reduced fat milk), beans, pulses, nuts, and seeds.