I spent four hours at the Canon booth, and they couldn't figure it out either until the second day when we discovered - and this is important - that the 600ex/rt on Master setting has to be on infrared (not radio) mode when using with a 580exII or 430exII. Little is known about this (because Canon really doesn't do a great job with instruction)
This is embarrassing for the Canon staff - with the 600rt display, most things are self-explaining. For using the 600rt with older optical remote flashes there's even a custom function to disable the radio part (and features that depend on it like group flash), so the 600rt basically behaves like a prettier 580ex2...
I wouldn't shoot events without the Gary Fong modifiers.
There seem to be very split opinions on this, and I'm not sure what diffuser to get. Some people saying these are extremely overpriced and you can re-create the collapsible Gary Fong with plastic for $1 yourself - but I guess that's paying for r&d.
But many people seem to rely on the less expensive and less bulky
Sto-fen Omni-Bounce - could you please share your experiences about the differences? Or do you have even both for different occasions?