Mark Hollman did a great job at describing the burn-up chart concept. I agree it is a great way to provide more insight to the team and whether their productivity vs. scope creep is having the greater impact on progress.
I did retort his point about motivation though.
My nugget: "... a burn-down goes to zero. It’s a floor that can’t be moved. A burn-up can keep going up. There’s no certain ceiling. It can be less motivating knowing that you are shooting for 50 today and tomorrow it’s 60. Zero is zero."