Used the 5D3 yesterday in conjunction with the mkii.
Hmmmmmm, what can I say. i always said the 5Dii was good and it still is but about half way through the day I was finding myself (if i have time) i would put the lens i want to shoot on the mkiii body rather than leave it on the mkii (if it is already on that) and I actually thought the mk3 makes the mk2 feel like a 30D, which I guess has more to do with the AF than anything.
Although I do notice 1 thing, I will need faster cards, it seems to fill up the buffer a lot sooner than the mk2. May be it was the SD card I have in it or something, but that is an Extreme card already which is the same speed as the CF. Odd.