The city itself is tiny, this is not the metropolitan area of San Francisco, its just the city limits, so yeah people in suburbs will commute into the city to work there, just like most other people working in San Francisco.
It is good for getting in and out, assuming you already have a way of getting to the Caltrain station which isn’t exactly in the center of the city.
Not even for the (sadly) semi-regular pedestrian fatalities that happen once or twice a month? Those usually delay trains for over an hour.
Caltrain's own reports say there are hundreds of late trains every month.
The last time was in 2018. I caught a Muni bus, the drive drove past someone at a stop who was in a wheelchair and was signalling to be picked up, another passenger challenged the driver, and the driver shouted something like "I don't want no cripple pee pee-ing on my bus"