I just used both of my 5D3s at a wedding last Saturday and they both have the firmware update. I shot 2,700 pictures with at least 1000 being in a very dark fast moving reception and I nailed just about every shot I took. There is a huge difference in the focus speed with the AF assist beam now. It once caused the focus to slow way down and now it speeds it up drastically.
That's great news, thanks for sharing!
I had a big photo shoot a couple of weeks ago (school yearbook portraits), using my 5D3 with the older 1.1.3 firmware, with an EF 100mm f/2.8L IS macro (tripod-mounted / IS off). I was using a four Speedlite setup (all 600EX-RT's), with the master in the hotshoe (non-firing), two more aimed into umbrellas and one illuminating the backdrop. I was running the camera from my laptop using the latest version of EOS Utility.
The room was otherwise dimly lit; a situation over which I had no control. The slowness of achieving AF was quite frustrating, but I just dealt with it and muddled through. I haven't had a chance to try out a similar setup since the firmware update, but am eager to do so.
On a positive note (somewhat off-topic), the ability to setup the 600EX-RTs without regard to line-of-sight to the master, and to tweak individual Speedlite output via the EOS Utility are fantastic!