Seth Godin mentioned Disney's technique of pushing work further. It's a worthy goal, yes, but did Disney have to describe it with a grammarian's nightmare like “plussing”? Why not “adding” or “pushing,” or “exceeding” or “going a step further”?
Sometimes, for ideas to stick, for a new concept to kick the block out of your head-gears and set 'em spinning, the idea has to be short, punchy, and memorable. Being able to say, “Plus?” at the end of a presentation might be the right kind of poke to represent a whole new way of working. “Add more” is too smooth, but verbing “plus” pops the track in your left brain, sending that train careering into your right.