Is there something about your current S95 that you don't like, or feel is lacking?
"Upgrade"? You won't get big bucks for your current cam, so the new S100 is going to cost
you... it isn't like you are trading in the barely used Ferrari 458 Italia for the next model. ;>)
My son has the S95, with which I've shot hundreds of exposures; it didn't seem to be lacking, for
the cam/size it is.
How often do you need to shoot at ISO 6400?
Comparo of two cams:
Side by Side Comparison: Digital Photography Review