Like I said, I'm sure they are very cool. It seems also like you can really gauge the kind of weight you are using, combining, etc..I do like the look of the chart giving you very concrete guidelines. And I use bands for all types of things. I don't pay money for anything that is not a multi-tasker
But they just wouldn't allow you to use accomodating resistance very easily is all.
Band pullups are a cool idea. I've never had to do it but I have seen it recommended and I've passed it on a couple of times.
Bands are just good in general, though, no matter what you buy