I love shooting in the theater when the light is sweet and the plays are interesting. I bought a Sony a57 just for shooting in low light. When I shoot it at 3200 the files look great at normal sizes. When I look at 100% I see some noise reduction smoothing at play. I had the camera set to "standard" noise reduction and shot Jpeg last Tuesday, at a dress rehearsal of Dividing the Estate.
I was using the Sony 70-200mm 2.8 G lens and I liked what I got. I might shoot raw the next time around just so I can try some other styles of noise reduction. The new version of Lightroom (4.1) seems to have well thought out noise reduction. I never seem to mind fine, monochromatic noise, it's only the splotchy color noise that I don't like. I noticed that the ISO 1600 shots I'd done with the a77 camera on the same evening cleaned up well. I shot them in raw.
I'm getting more and more comfortable with the EVF in the a57. I know it will nail the exposures and I'm getting a handle on the qualitative differences between the contrast on screen and the contrast in real life. While the EVF is not as good as the one in the a77 it's acceptable. And the nice part of the compromise is that even the raw files from the a57 are easier to handle than those from the a77. Post processing 1,000 images from three cameras shows you just how much more time nearly doubling the shooting file size takes on the backend.