I have a 5d3 and I am contemplating purchasing the Canon 430 EXII, and Pocket Wizard's Flex and Mini for off-camera setup. As far as I know you can access all functions of a flash (including ETTL) using the flex/mini combo as if the flash is mounted on the camera. Please correct me if I am wrong. Are there any cheaper but reliable alternatives?
Also, in case of 2 off-camera flash units what setup will I need then to be able to control the flash functions directly from my camera ? Can I make do with 2 430exII's or will I need one 580 unit as the master? Assuming both flashes are off-camera. Hope I made sense.
I'm still debating this as well. I'm currently using cheap non-TTL triggers and the optical system that Canon provides for ETTL.
For line-of sight you'd need a 580 or the ST-E2 (or knock-off). You're idea about the PW should work. There are a few things to consider in my experience:
ETTL with PW can be the source of some unique problems, starting with interference all the way to reports of 580EXII flashes blowing out when used a lot with their version of HSS. Other people say that they are perfectly fine and there are no issues. Alternatively, there are the Odins already mentioned here. For people interested mostly in ETTL style shooting and/or a desire to access auto or manual functions wireless, these seem to be a better option. The transmitter and its manual look really nice. But since nothing is ever perfect you have to consider if you'll ever use your speedlites together with studio flash. You can't turn the preflash off on the Odin system - even when in manual. Without that issue I would have bought them already.
So what alternatives are left? One thing that I'm personally leaning towards right now is to just bag the whole ETTL option and go with a bunch of PW Plus III. Why? Because I find that ETTL seems nice at first and is very good for some things - but if you want a controlled environment it's better to go manual anyway. Would it be nice to have HSS? Yes (still available with line of sight of course and that actually works better than its reputation would let you believe, even in daylight and sunlight). Would it be nice to set the manual setting via the camera menu? Absolutely. So yes, the Flex and Mini will do that. Just make sure you read up on all the details for your specific needs and where you want to go in the future.
With the new 5DIII there is always the option to invest in the new Canon wireless system and call it a day. Seems really really nice albeit expensive still.