With m-audio boards, you can program any sliders and knobs to basically do what you want. However, i have to be quite honest in the fact that i found very quickly that it was easier to just use a mouse most of the time. I have an m-audio axiom that has alot of features but i'm just using it like a regular old board. I find it's often easier to use a mouse, plus i forget what does what. However, i do use my knobs for automation, that's very convient. I just use one though and just assign it as needed.
If you are using external sound modules, i find controllers to be very convient. You can just go through sounds right off the board instead of going to the module, turning a knob or pressing a button, get back on the board, and repeat until you have the right sounds. Plus, once you are familar with the module, just punch in a number and the sound comes up.
I also like pads for both drums and sampling. I think it's worthwhile. Anyway, i don't use
my axiom to the fullest at all but i still love it. Their are many similar keyboards with similar functions from various brands. Even though i don't take advantage of many things, what i do take advantage of has been worth while over my really basic board i used before this one.