In a full week of usage, I've yet to run into any actual, material problems with the new maps (daily usage in San Francisco). I'm using The Transit App for transit directions, and it integrates nicely. Sometimes business locations are 10-20 yards off, but that's about it. I've already noticed some of the problems I've reported getting fixed.

Depending on where you live, I think you'll find all the peanut gallery moaning about the new maps to be a bit exaggerated. Try actually using it for a while. It's decent (at least where I am).

(In fact, the new iOS maps are a godsend for transit directions in San Francisco. iOS 5's transit directions use the "scheduled" times instead of their actual times. If you've ever been to SF, you'll know that busses and trains don't even try to operate on a schedule -- they just come and go whenever. With iOS 6, I can use an app that uses their actual times -- The Transit App. I'm much happier with this setup, even though it requires an extra tap to select the app when getting directions.)