I attended my 6-year-old son's Christmas play yesterday. Found that to get acceptable shutter speeds with my 70-200 f/2.8L IS, I had to bump to ISO 3200. Didn't want to do it, but I figured a noisy shot is still better than no shot at all.
I was impressed!
Not all images embedded, but links are there.
And then 2-pictures stitched together: