Boy, Clif Bars came up with a winner here. There's a nice chewy texture, with a hint of crunch, and lots of chocolate with just the right amount of mint. I'd say they're sustaining but that's true of most protein bars. It's not a substitute for a salad, but it will keep you going when you need a quick bite. You might want to buy two boxes, because a person can go through one box really fast.
This is my favorite Clif Bar! Unfortunately, synthetic caffeine makes me jittery and causes some joint pain. So, I can't really enjoy them on a regular basis. But it is one of the best tastes I've experienced.
For Clif bars in general--I'd like to think that the better quality isn't enough reason to pay so much money. But when I eat a cheap snack bar with junk ingredients while doing a workout or something that requires my physical or mental best, the difference is clear. Sometimes, it's worth the extra money.