Cannot play "Tain't It The Truth" by Ernie Kado, or "Smack Dab In The Middle" By Ray Charles. It's impossible with out the Sync/Stop button.
I have it on the foot petal but some times I forget and hit the button with my right hand.

It also helps to play "Ain't That A Shame" Fats Domino.

There's lots of tunes where this feature comes in handy I'm sure. The foot petal helps a lot.