I have to say that, if you are considering upgrading to the 600EX-RT, it is AWESOME. I previously had two 580EX's and the PW flex/mini combo. What a disaster. Between the interference issues, trying to remember the order to power everything up between camera, flash & PWs, all the batteries, it was a hassle. Given, if you go OCF alot, you don't need to relearn the learning curve every time. But for the occassional OCF guy like me, I spent more time setting everything up and re-learning it than I did taking shots. I became discouraged. I sold all that stuff to upgrade to a better way.
This morning I started playing with the 600EX-RT and ST-E3-RT companion remote. What a treat this was! It just 'works' and it works great. And aside from that, I have an existing MT-24EX and using that ring flash as a master and 600EX-RT as the optical slave is flawless. Simply cycling through the link button changes from radio slave to optical slave. Obviously the ring flash is an optical master - Im talking about how easy it is to switch between radio and optical OCF.
Anyway just talking out loud to share my experience. I plan on going OCF much more given the ease of use of these flashes / accessories.