These are GPS issues you are having, nothing to do with the maps. When the navigation software receives a GPS signal that places you in the field rather than on the road, it can do 2 things - either place you exactly on the spot where the GPS says (the field), or assume that you are driving on the nearest road. The latter may not necessarily be on the actual road you are on, so it's not exactly the better solution. I've had those issues with all navigation softwares I have (starting with the Google based former maps), they all work much better when the iPhone is plugged into the Magellan car dock I have, which feeds the iPhone with more accurate GPS data from its more powerful GPS receiver.
The more I'm reading about this, the more tired and annoyed I am. If somehow every phone owner in the world, on one particular day (like Sep 21 2012, when iOS6 was released) ganged up on Google Maps and decided to publish all the problems they've had with it, the servers wouldn't stand the load. Apple Maps is doing actually quite well with the crybaby assault.