They've called the S400 a "break-through" camera.
I started with the Elph series with the S100 years ago. It was trusty and traveled up countless climbs with me. I ultimately replaced it with the S400 which gave me the ability to shoot all day with one battery as well as travel with me to 30 meters below the sea (with the underwater housing, of course). Now it is gone. I love my SLR but I just can't seem to fit it into my pocket!
When I saw Alan's S400, I missed mine, feeling very guilty for doing it in by dropping it.
They say the best camera is the one you have with you. If that is true, then the S400 had been my "best camera" for a long time.