Here is my 3-week update: I am liking these new cameras. The front camera is very, very clear, sharp and bright. It helps when pulling nose into a space to avoid the bump-and-feel method of parking. It is easy to press and hold the radio power button for 7 seconds to activate the front camera. It will stay on the front camera view until you turn it off or go into another gear. I have also gotten used to, when stationary but wanting to see the front camera view, popping the truck into R, then D and the front camera will come on, but only for a few seconds.
The side cameras are on whenever the turn signals are on. This helps a ton when changing lanes - blind spots eliminated - or when stopped and ready to turn, you can see the bicyclists who feel the rules of the road only apply to you and they are now in the blind spot.
I did call CameraSource and the harness builder asking if there is a way to activate the side cameras with the 7 second radio power button method. I thought it might be nice to turn the side cams on without having the turn signal on. Turns out you can do this, with a small modification.
1. Add an RCA splitter to the left or right camera feed behind the dash, plugging the new free end into the open "video" feed of the harness.
2. Press the left-most left arrow on the steering wheel for 12 seconds.
This turns on the system to accept a third camera feed. If you activate the front camera with the 7 second press, it will now let you toggle not just front to rear camera, but also front to rear to side camera.
I'm not going to do this (yet) but am happy to have learned it can be done.
Summary - great front and side cameras. Easy to turn on the front when needed. Side cameras are on when the turn signal is on for that side. You can add an RCA splitter and get one of the side cameras to be available when turning on the front camera.