I've been bringing less gear for actual day shoots - you can't beat the reach or the comfort in having a telephoto or telephoto zoom at the ready on a second body, but you sure can move closer a lot quicker without that lump of glass on your shoulder.
As the second photographer I had the luxury to shoot with two lights - quick 'n dirty with two 580EXIIs, the off-camera flash being attached to a Justin clamp and triggered by the on-camera master.
It's a hit-or-miss affair more often than I would care for, but more so with regard to positioning than exposure. Times like these, the old 580EX is preferred to its Mark II replacement- switching between Master and non-wireless mode is unnecessarily painful with the latter.