after reading this thread, maybe people have unrealistic expectations about their gear. Hell, I shoot a 5D2 and outer points the majority of the time, but when it's dark, center point and even manual focus when needed. I figure the 5D3 outer points can only be better than the 5D2 a certain number of EV's, so in a lot of low light situations, it's a no go.
That's a good thing to keep in mind and sound advice on how to cope in low light situations--the center point is still more sensitive than even the cross-type outer points on the 5DIII as well, although now there are 2 AF points above and 2 below it that are as sensitive per the AF literature--but I don't think that's what's in view here. People are seeing this problem in all kinds of light levels, and conversely people without the problem have reported that the outer points work reliably even in low light situations although of course not in as low light as the center point does.