As for safety, all we really need is for them to be safer than the average human driver. As evinced by the ~40,000 road deaths every year in the US, that's really a pretty low bar. I'd even argue that full autonomous is/will be less risky than halfway houses like Tesla Autopilot where neither side is really in full control, but that's another story.
It's ready/safe when governments ("the people") decide it's such.
https://storage.googleapis.com/sdc-prod/v1/safety-report/Way...
They've been very careful about it, and they have not finished work on it, so they need to keep the same standard that they had until now.
The technology is also ready for Phoenix. The company is not yet ready for the whole world (but I have no specific insight into what's holding them back).
It's totally different from Uber.