It's a PITA and with only a 3% efficiency savings.
So consider you spend $2,400 a year on gas. That's a $72 savings per annum. To me it's not worth the hassle of start/stop.
Especially in hot weather it turns off the a/c condenser so although the fan blows it gets hot quick.
In a major traffic jam I might use it as I'd think excessive traffic would yield more than 3% savings.