No, it doesn't have to be 'almost perfect'. Significantly better than what we have now (people with emotions and imperfect decision-making, ranging from 19 year-old newbie drivers, 45 year old over-confident CEOs with their SUVs driving in the city to 82 year old drivers who can barely walk so would rather drive) is already a HUGE improvement.
"self-driving cars is" not the same as "anti-gravity technology". People - including many innocent people - get killed every day because of reckless driving or human mistakes. People-driven cars also needs more infrastructure - more signs, more roadblocks / infrastructure, cluttering up the city, making it less human-friendly. Cars clog up the city, because people don't want to drive too far to work.
Concerning safety and making cities more livable, I only see upsides for autonomous cars. People can work in their cars coming from outside the city. The cars are safer and more reliable. There's less cluttering in the city (e.g. an intersection with 10 signs for each corner), because cars can also communicate in non-visual ways.
Plus we've made significant headway and it's not a fantasy anymore.
"anti-gravity technology"... is just a random technology. A solution looking for problems to solve, I suppose. With positive and negative consequences.