I use quadfire and the load is even across all GPUs.
What is this obsession I keep reading from some people regarding it must be 99% usage for CrossFire to be worthwhile? so many that I've read seem to be so focussed on is 99% usage = great fps.
Upon my own checking the usage only climbs the more action happens on screen and has no bearing on the fps. I've seen some of the streets with little action and the usage could be 45 - 55% but soon as the action hits I've seen it reach 85 - 90% and my fans speed starts to climb. Thats also why I keep vsync on due to the noise.
The load is also even on my two 5870's.