Admittedly, I haven't used the new Maps app, but only because I've avoided upgrading my phone to iOS6 solely because I've heard the new Maps is so terrible.
Our personal, relatively microscopic sample sizes are the problem with the sentiment on this. I've used them in Florida, South Carolina, and North Carolina, and they worked fine for restaurants, turn-by-turn, etc.
As others have said, a combination of the vocal minority and the human race's love for drama is what's keeping this discussion alive.
Just out of curiosity, after I got back, I upgraded my iPad to iOS 6 to see whether all the complaints I'd read about Apple's maps were legit. Then I went and looked up a bunch of the places we'd traveled or stayed in Ireland, to see if the new maps would have gotten the job done. Short story, it would have been a lot harder. In the spot checks I did, the roads are there, and in one case the driving directions are better than what Google recommended, but it mostly didn't know what I was talking about when I searched for businesses, like hotels we stayed at.
Google has amassed a huge amount of really high quality data, not just roads but also businesses and places, which nobody else has. I don't know if there's widespread appreciation for how hard this is and how hard Google's been working on it (one example, and I'm sure this article is slightly politicized and the timing of it appearing now is no coincidence, but still, it's mostly fact: http://www.theatlantic.com/technology/archive/2012/09/how-go...). Hopefully Apple has the staying power to go amass the same data, but it's an uphill battle.
People conveniently forget how Google Map, Nokia Drive, and all others let you down on a regular basis, and how much room there is for competition in that market. Street layout is mostly right in all apps. POI however is a joke in all of them. In the city of London, Google Map only has a fraction of the shops and there is no logic which one it has and has not. I does not have the Starbuck(!) in front of my job, but it has the clothes shop next to it and nothing else in the street. Nokia Drive keep sending me on farm/field trail when I'm in Spain. At the same place Google Map has random missing road or missing portion of road (those road have been there for 200+ years like the house built on it). I briefly tries IOS Map at the Apple Store and it has the correct layout but only label some of the road, making it equally useless IMO.
We are planning a trip to Japan with Google Maps right now. It is convenient only because of its interface - but really kinrin (something like that) is incredibly better at showing stuff that matters.
The app I used, http://itunes.apple.com/us/app/transit-directions-public/id5... was pretty bad on iOS 6 launch day (with instructions like "take a bus", without mentioning the line), but a week later improved to be perfectly usable here in Switzerland.
I haven't had any trouble at all with them here in New England, FWIW.
Don't make generalized statements unless you can back it up with data.
I've had no issues since I started using the beta around the Southeast US. I've used it from Tennessee to Florida, with turn-by-turn directions around the Atlanta area, to Orlando, all over Disney World, and more.
Let's not contribute consensus where consensus isn't due.
In Finland, a guy I know got directions that told him to go through a road that hasn't existed for 6 years.
Also, most of the market for iPhone users are city-dwellers, and most of those don't own cars. Having good timetable/route planner for public transit is very important. As I understand, Maps doesn't work for that at all.