I agree with Gary. Pushing ISO 100 two stops is not better than shooting at ISO 400. It works, but it's not better. However, my XSi only goes to 1600 ISO, so when I need more speed, I push it to 3200 ISO and get reasonably good results. Makes me wonder why they didn't offer it in-camera, because I'm sure it would be even better. Stupid marketing department.

Paul