Well I've got 30 days to try it so I should know if its a fit by then. I'll try and keep everyone updated.
By no means is the AF bad, it's just that the 51 AF point module is so good. It was just weird to use an AF system originally meant for DX/APS-C on a premium Nikon body.
The battery isn't bad by itself either since it's quite compact, the problem is when you have other Nikon DSLRs all running the same battery, except the Df. Plus they were able to fit the en-el15 in a Nikon 1 V1 body, so they easily could of fit it in the Df.