I have used a ton of ON in my lifetime. The Extreme Milk Chocolate is a definite favorite. Trying out the Mocha Cappucino these days. It's decent. Disliked many of the other flavors.
Gram for gram, protein powder is still cheaper then cuts of meat, milk or cheeses around my neck of the woods. So I figure it's already cheaper / saving money whenever I have a shake. Nevertheless -- still good to get your protein from real sources of food.
I have tried a handful of protein powder brands, too. So far Trutein Cinnabun sticks out as a favorite. It really deserves the reputation it has in my view. It's decadent and has a good nutritional profile (not as carb rich as some of the other tasty protein powders).