Aside from the above (joint stress issues) working against bands provides an overspeed eccentric which can lead to building a better bar turn around speed.
Working against bands also is great for speed work as it provides contrast such that you don't have to slow down (stop applying as much force) as you approach the top of the lift.
Reverse bands in my opinion aren't real good for speed work, but I think they are fantastic for overload work (getting a feel for weights heavier than you can handle for 1 rep), or specific weak point work (bench/deadlift lockout, and if set-up correctly can really be used to hammer the upper-back on the squat with a safety bar), or for training for gear.
That said, I do like to deadlift/rack or block pull against a lot of band tension, but not squat or bench (it just feels bad to me). It just kind of feels right and I like the contrast and grip work from it.