A couple months ago I shot the finish line of a local 10k. As you can see the end of the race was, uhm, pretty dark. There was a construction site generator with flood system behind me, but I still had to crank my ISO up to 8000 and that made me pretty nervous. Another company did the editing and I was impressed. They said they added a very small amount of noise reduction.
I never looked at the original photos on my memory card until tonight. We were to shoot medium jpg. This is slightly cropped, but otherwise it is straight out of the camera. I have to say that I'm OK with that high of an ISO on this type of shot.