Having owned, programmed extensively, and used a 710 and two of the 600's for several years now, I recently purchased and set up the 620. I find the extra buttons very useful.
My Denon receiver has 8 inputs, and the 620 has 8 Device Control buttons. I set it up so that holding down each button launches an activity associated with the corresponding input.
There are four System Control buttons. Button 4 executes a macro to shut everything off.
All is wonderful so far.
Buttons 1 through 3 each execute macros for the three of the eight most-used activities, so they are copies of the macros on three of the Device Control buttons, but despite being exact copies, they don't do the same thing!
At the end of the macro the last button pressed is the corresponding Device Control button, with the purpose of leaving the remote control in the state where it controls that device. But when the System Control buttons are used to execute these macros they don't do that! They leave the remote in a state where it's controlling whatever device it was set to control before the macro was executed.