None of this is an excuse for this extremely bad decision to ship it in the 1st place. It wasn't even shipped as a beta product, but as a full-blown replacement for a fully functional app that people rely on every day. I know it sounds a bit over-dramatic but people are being directed up one-way streets, onto non-existent streets, illegal turns etc. This could be problematic especially at night when you might realize the error too late - yes someone can actually get hurt or killed.
And I don't buy the 99% claim at all. Did Apple calculate how much of the data is actually valid? No of course not, how could they? When they released it I'm sure they were convinced it was 99.999% accurate.
What really gets me is how Apple essentially admitted Maps is a failure and people should be using competing products, yet you still find Apple fans claiming it isn't that bad or that people are over-reacting. Which part of "Apple just admitted it is a POS" don't they get?
EDIT: It's not just that the data is inaccurate, it's also that the routing is borked. There are screenshots of routing that takes you miles away into the opposite direction to some imaginary destination while the actual destination is clearly marked with the red pin within a mile of the starting location. I guess Apple though mapping was easy, or that their engineers were smart enough to get it right in a short amount of time.