Took the plunge and have the second 600Ex RT unit and have covered two shoots with it so far. So simple to use and ratio between the two heads on the fly. Can't wait until they bring out the 450EX RT unit to add the finishing touch to my speedlight set up. Bowens units will spend more time in the studio and location projects become far less stressfull.
The Canon rebates mean that they have cost around £450 eaxch inc vat, so does not compare too badly with the 580EX units I bought 7+ years ago for £360 each!