two flashes create one light with twice the power of one flash. And if you run them at half power you get the same amount of light as one flash at full power, but way faster recycling and much shorter duration so action is a lot less blurry.
I haven't used it but as long as you're not concerned about shooting around corners or in bright daylight it should work really well. I've used Nikon's remote iTTL and it works fine as long as you're close enough with direct line of sight between master and remotes.
I was at a race here in Scotland shooting and I saw a guy with flashes in same position pointing in the same direction, what exactly does that do? surely one flash cancels out any effect of the other