Like Doug, I've consumed a lot of Perpetuem in the last couple of years. I've got a couple of observations to add:
1) I prefer it mixed thick and then consumed with plain water.
2) Perhaps due to the protein and/or fat content, it is *far* more palatable when it is cold. The Dreamsicle flavor is downright tasty when it's cold; warm Perpetuem is, shall we say, an acquired taste.
3) I've found it difficult to get it to dissolve completely when mixing. It tends to form clumps easily.
4) For an alternative along the same liquid nutrition lines, I'd check out InfinIT Nutrition. Their stuff mixes mixes easily, and is drinkable when it's warm. Plus, you can customize your formula -- adjusting the amount of carbs, electrolytes, protein, caffeine, even flavor you want. It's my current fuel of choice for done-in-a-day activities.