Never had issues nailing focus during weddings with my Sony cameras personally. I think a lot comes from knowing the camera. I’ve used Canon 1D’s in the past and the A9 was/is absolutely the best focusing camera I’ve ever used hands down.Right now I solve the AF issue by just having a Nikon too. For weddings you still really can't beat a Nikon AF system. Even the Sony A9 series doesn't have IR AF for dark receptions. Until that changes, wedding peeps like me will probably have a mirrorless and a DSLR, or no mirrorless at all.
Personally I am just loving my S1R, and I look forward to the future of the system.
I don’t expect every autofocus system to be perfect all the time but I do expect reasonable speed and accuracy.