I now understand your zoom concern and would declare it a non issue.
I only zoom once per dive so it does not really matter how slow it is. So i do not worry about it as it is not a feature i use regularly. At the start of each dive I turn my camera on and then zoom it all the way and leave it there. Since I shoot mostly macro, I often never change the zoom during a dive.
I worry more about focus lock, flash recharge and image storage cycle times. These features come into play much more often than zooming. They are important, zoom speed is not.
Something that has helped me in making decisions is to create a prioritized list of features based upon my intended use. Items like zoom speed fall fairly far down the list. They are in the "who cares" zone so I feel happy ignoring them.
Concentrate on the important issues. You will not find a "perfect" p&s camera that out performs all the competition in every area.
But now that you have started bringing up these other issues, I think the color of the g15 is not a real "canon black". It appears to have a slight green tinge to it more like a Nikon...