I put 4 admin buttons on my CP. I think they're very handy. I use pause all the time. Exit is very useful as well, as I didn't want to use standard shifted buttons for that. Before I set up a button for that, I had already exited out of a few games using the defaults. I currently use the other two admin buttons for save and load state, which is most handy on the console emulators.
My pause button is my shift button (ipac). There's no problem doing this, because as long as you hit a another key while holding down the shift key, you won't perform the standard function of that key. So if you pause, hit shift-something, you'll still be paused when you let go of the button.
I don't use the default MAME keys on my ipac, so I also programmed shifted functions for the arrow keys, tab, and enter. The rare times I need to change settings in the game I can do so without breaking out the keyboard. This wasn't necessary, but with all those shift functions you can program, I figured I might as well assign some of them for a useful purpose.