My dad is an on-call doctor; getting to his hospital by car takes ~15 minutes, but ~60–90 via public transit. His patients don't have the luxury of waiting for him to take the bus. His hospital is outside of this zone, but I imagine that paying $15 every time he got called in would be extraordinarily frustrating.
My mom does work within this zone, also in places not easily reachable by public transit. I suspect that she, like many others, will still commute into Manhattan, park in areas outside of the zone, then take public transit into it — which will increase congestion in those areas. It'll be interesting to watch for the lead-on effects.
I sympathize entirely with the desire to reduce traffic in the city, but man, for people who live far from work and can't easily commute any other way, what a pain.