I'd say that aside from the terrible batch of Peanut Butter isolate I just got, the stuff is really great, taste-wise. The Cinnamon Bun, Cupcake Batter, Banana, Egg Nog, and Chocolate Peanut Butter Cup flavors that I bought were all awesome. I usually mix a scoop with 6 oz of water and immediately shake it up in a jar and it mixes really well. The trick is to shake it up IMMEDIATELY if you want to avoid clumps in your shake. Mixing the scoop with 6 oz of milk tastes even better.
Before ATW, I had tried Optimum Nutrition and I also recently bought a batch of Dymatize Elite Gourmet protein. In my opinion, All The Whey beats them both as far as taste (aside from my one bad batch of plain peanut butter).