I've been comparing cameras for a few weeks now, and here are my thoughts on the G6 vs 8800 comparison:
Both will produce excellent pictures, but I'd give a slight edge to the G6 for less noise at iso settings above 100. If you don't need the long zoom range and VR of the 8800, then the G6 is probably a better choice. Ididn't findthe AF speed and shutter response to be significantly different. One shortcoming with the G6 is that the LCD screen is very dim in bright daylight, and since I always use the LCD for composing my pictures, it's a serious shortcoming for me.... it may not bother you as much.
The optical viewer on the G6 has lots of parallax error. It's ok for landscapes, but not really suitable for macro.
If the G6 meets your needs, I think you'll be very happy with it...