Well, the new 1DX and my f/1.2 50mm lens work well even at a party, taking pictures in the dark. I have it set to 1/250th second min exposure and 25,600 max ISO and all on auto. This shot was f/1.4 1/250s ISO 8,000. Fast moving people with no flash and still getting a reasonable shot.
The focus did take a moment, understandably, but it did auto-focus even in very low light.
Over all, we got a few good pictures from the party. Adam clearly has no concept of the meaning of "Over the top"... :-)
The GPS worked indoors with no problems, and goe-tagged shots nicely, including which direction I was facing. The WiFi uploaded shots as taken, and so I was able to show people pictures on the iPad right away. Nice when the technology works!
I did not stay to the end, sorry - got a bit of a headache.