So I have the 5D3. What about your experience with the upgrade?
How does your "hit rate" compare between the cameras?
I'll be upgrading AND keeping the 1D4. I love this camera and value the APS-H sensor.
Other than APS-H, the only significant thing I'll miss from the 1D4 is the illuminated red AF points.
But it's the sheer power of the AF that is a prime attraction of the 1DX for the way I work. After working for a few months with the 5D3 I think I have some reality on the AF capabilities of the 1DX. Plenty of others have had very high expectations and not been disappointed.
Cameras: 1DXII,5D III, 5D II. Lenses 24-70 2.8L II IS, 70-200 f4L IS, 70-200 f2.8L IS II, EF 400 5.6L, 300 2.8 IS II, Samyang 14 mm 2.8. Flashes: 600EX-RT X 2, ST-E3-RT, 580 EX II.
Plus lots of stuff that just didn't work for me