I got the 24-70 L II on thursday here in Germany and tested it today against my Canon 85L, the new Tamron 24-70 with IS and the Canon 35L.
The 24-70 L II is sharper than any of that lenses at f/2,8. Only the bokeh of the 35L and 85L at f/2,8 looks for me nicer (especially at f1,4 / f1,2 of course, but also at f/2,8).
But consider that the 35L costs only about the half of the Canon 24-70 L II and the 24-70 L II is sharper, but not that much, that I would pay 1.000 € for this little more sharpness in comparsion. On the other side the Tamron costs also 1.000 € less than the 24-70 L II, but is only sharp in the center at f/2,8 and very unsharp in the corners. This is so extremely that I am willed pay 1.000 € more for that 24-70 L II.
The value of 35L for me is the low-light-capability im combination with my 5D3. But since today I love also the new 24-70 L II and will sell my Tamron as soon as possible.