There is no doubt that Quest bars are the best quality protein bars around: they are high in fiber (about 17% on average, all soluble fiber which is preferable), relatively low in fat (8-10%), and high in protein (about 20%), with no Maltitol or Sorbitol (these are very common in protein bars and can cause severe stomach pain and very unpleasant flatulence). I have tried a lot of bars and don't see any with this sort of nutritional profile.
However I confess to disliking many of the Quest flavours, either because they taste too strongly of Stevia (the new, 'all natural' range) or because the flavour is rather sickly. A lot of people on the internet say that if you microwave them they are much better but the point of having a bar, for me, is that I can take it anywhere with me and eat it on the go (for example instead of the biscuits or sandwiches that are so ubiquitous at meetings), so the need for a microwave rather defeats the purpose.
The Peanut Butter Supreme is amongst the exceptions: the sweet/salt balance is just right, and it tastes of... peanut butter. There are small chunks of peanuts in it and it's not rock solid like the Double chocolate bars for ex. There are two more peanut butter types in the Quest range and this is by far the best in my view, although Peanut butter and Jelly is OK. The other bars which in my opinion gets the balance of salty and sweet right (which is very important, otherwise the bar tastes sickly sweet) are Vanilla Almond Crunch and Cookie Dough and Chocolate Chunks (the latter has really big chocolate chunks and a very good texture). Finally, Cookies and Cream is different because it has a more tender and crumbly texture. It has pieces of what looks like Oreo cookies in it (but it's not really Oreos) and that gives it a really nice texture. The taste is also OK.
Hunger-wise they are quite amazing because contrary to many protein bars (such as Atkins, for ex, which gave me terrible wind and caused cravings), they really do fill you up. I don't react to them as I do to candy bars or other (palatable) protein bars in the sense that I find it easy to stop after one, or half one. You need to drink a lot of water with them (the fiber) but they keep you full for a long time and prevent uncontrollable feelings of hunger. I am not diabetic and thus do not have the equipment to measure my blood sugar but based on subjective experience I am pretty sure that they do not cause any spike in insulin, neither immediately after eating them, nor 1 or 2h later.
Finding these has made a real difference in the management of my diet (I'm neither overweight nor a body builder, I'm just trying to eat in a way that allows me to keep the weight I have and not feel deprived).