Not all stop/start systems are created equal. I found the system in my ST to have two issues.
1) The starting motor is noisy when it starts. It stutters and causes my ST to lurch forward slightly against the brakes when it turns on the vehicle at a red light. The lurch forward can be enough to move your head back slightly while sitting at a red light.
2) There is a delay from the time you touch the gas pedal to the time the vehicle starts rolling. This causes concern if I need to accelerate quickly when making a left turn into oncoming traffic at an intersection.
Comparison: I have rented other brands that all have the start-stop feature and some don't have a shutter or a delay at startup. For example, I rented a Chevy Malibu for a business trip and it was quite on the start, and had no delay on acceleration.
Doing a little research I see that this is a known issue with various brands. So, unfortunately, I think my ST is on the poor side of the Start-Stop execution.
https://www.cars.com/articles/which-cars-have-the-best-stop-start-systems-1420684556033/
This is another example to me that my ST is brilliant in the concept, design, and performance (why I bought it). But poor on the execution of the systems and build.