It was very overcast/shady today and I switched to the 1DX to see how it would handle the conditions.....the high ISO images really clean up so nice it is surprising. Much better than the 1D MKIV. My biggest wish is that I would like it to have the same pixel density as the 1DMKIV.

1DX
700mm
ISO 6400
f/5.6
1/1000