Overall, I think they are just overpriced meal replacement bars. They have a lot of fiber, but a measly 5-6 grams of protein (the fullbar fits have 15 grams, but that's still not as much as you can get from many other foods). They also don't have very many nutrients for their 170 or so calories (e.g. very little vitamin A, vitamin C, calcium and iron) and, in my opinion, this basically makes them empty calories. On the good side, they aren't totally loaded with sodium, like so many other processed foods these days.
I think that you could do a lot better by choosing your own foods (get just as much fiber, a lot more nutrients, a lot more protein, etc.) and I think that you could choose foods which would leave you feeling just as full/satisfied. If you would be interested in suggestions as to what foods to choose, I know you would get a ton of suggestions from everyone here just for the asking.
I also have to ask these questions:
If the fullbars work and are an effective tool to help people lose weight, then why is the weight loss surgeon who invented them still performing weight loss surgeries on people? Why doesn't he just give his patients fullbars instead?