Originally Posted by AKMac
This is an interesting question. I used to often D&B on individual channels with one window (active) open as the target channel, and a second window showing the RGB results. I stopped doing this a while back because when I upgraded (I think it was to CS6) I couldn't seem to get the two independent windows(single channel view and RGB) up any more.
At that time the shortcuts Cmd 1,2,3 and tilde referred to R,G,B and RGB respectively.
FYI, with the release of CS4 or CS5, Adobe made a number of disruptive changes to some of the most important shortcuts. Ctrl ~,1,2,3 is now Crtl 2,3,4,5 respectively.