It has been awhile since I have updated this thread with new observations about the G15. This afternoon a few things that I discovered early on though came to mind so I will add comments about them.
With this camera I usually have it set to Program mode since generally I don't care a whole lot about the particular aperture (unlike with larger sensor cameras which I always choose the aperture) since the DOF is rather deep even wide open and the lens is good wide open. I also usually use Auto ISO. The G15's Auto ISO is pretty good. You can set the maximum ISO that it can use up to ISO 1600 (minimum ISO is always 80). When not using Auto ISO you can go up to ISO 12,800. With Auto ISO you can also set the Rate of Change (Slow, Standard, Fast). I generally use Standard, but sometimes use Fast. When using Fast the camera will often bump the ISO up a bit more which gives a faster shutter speed. That comes in handy sometimes when doing street photography because otherwise the camera sometimes will choose a lower ISO (for better quality), hence a slower shutter speed and sometimes you might have a better chance to getting subject blur. It is nice to be able to adjust these things. I have thought about in these situations using Av mode and just setting the widest aperture to ensure the fastest shutter speed, but generally that isn't necessary.
You can configure the front and rear control wheels to various functions and they can be different for P, Av, Tv, M modes. I have the front control wheel configured to zoom to specific focal lengths (28mm, 35mm, 50mm, 85mm, 100mm, 140mm) with each click. You can still use the zoom control which zooms continuously. While on the street I use it a lot. Before bringing the camera to my eye, which announces to the world that I am about to take a photo, I very quickly use the front dial to get to my guesstimate of the approximate focal length I want. At the same time I often quickly dial in a bit of exposure comp based on the scene and my guesstimate of how the meter will react. When necessary I do both of these things pretty fast while the camera is still down. Also, if you use the front control wheel to set the focal length the camera remembers it when you turn the camera off. When you turn the camera on it returns to that focal length. Nice touch. When you adjust the zoom using the regular control the focal length is reset to 28mm whenever you turn on the camera.
Besides the ability to configure the front and rear control dials you can configure the rear button. I have it set to switch between raw and jpeg.
There are 2 custom settings on the mode dial. I have mine set exactly the same except that one uses Auto ISO Standard and one uses Auto ISO Fast. It is much easier and faster to quickly move the mode dial than go into the Func menu.
The G15 raw files are a bit large. My understanding is that both my E-M5 and G15 produce raw files with lossless compression, but even though the E-M5 has 1/3 more megapixels and the embedded jpeg has significantly more megapixels the G15 usually has larger raw files:
E-M5: 16.1mp, 12-bit, 4640x3472 with embedded 3200x2400 jpeg -- ~13-15mb
G15: 12.1mp, 12-bit, 4048x3048 with embedded 1600x1200 jpeg -- ~12-18.5mb
Taking a nap downtown today: