To Jayson-
By and large, most radio flash triggering solutions only transmit one command, "FIRE!!" You have to adjust the flash power manually (either by adjusting the output of the flash, or by adjusting the distance of the flash to the subject). It takes some getting used to, but it works great once you get the hang of it.
The new PocketWizard Flex units will transmit ETTL data so that you can adjust your flash units from a master flash on your camera. That said, the earliest reports indicate that PocketWizards somewhat rushed the product to the market before fully testing them. The reliability and range of the units seem to be very "un-PocketWizards-like." The RadioPopper PX system transmits the ETTL data as well, and they have quite a loyal following. The only complaints with RadioPopper PX units usually focus on the mounting (the receiver units must be mounted to the flash in order to work properly). RadioPoppers are going to address that issue soon enough when they release a bracket mount that will make the standard issue velcro a thing of the past.
Now, the biggest problem with using the new PocketWizard Flex and RadioPopper PX units is that they require you to buy expensive flashes. For the price of one 580EX II, I can buy 3 cheaper flashes that don't have ETTL capabilities.