just what is "intensity"?
Did you see this?
--intensity|-I Intensity of GPU scanning (d or -10 -> 10, default: d to maintain desktop interactivity)
and what does that mean? how does it affect miner output?
Its like priority in the windows task manager, it sets how important the hashing is to the GPU. 'd' setting is good for computers being used while mining, while most dedicated mining cards see performance benefits in the 9-15 intensity range, from what I've seen.