Tamron 24-70 2.8 VC

Hello,

Would anyone be able to provide input on how sharp the new Tamron 24-70 2.8 VC lens is, and compared to its competition:

Sony CZ 24-70 2.8
Nikon 24-70 2.8

It would be for the D800, in which I would get the Nikon 24-120 F4, which peformed well on the D800. So I'm just trying to see if the new Tamron should make me change my mind about getting the 24-120.

Thanks for any input.