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Like all iPhone 5 users (and most developers) I've been using iOS6 for a while now. Overall, I find it great - it's fast, consistent, and generally a good upgrade. It's more like iOS5.5, really, but thats a side point - the naming doesn't matter much.
There is, however, a huge amount of heat going on the maps app. No point in rehashing it, or even linking to it, it's been all over the place.
I think there are two issues here, and they need to be dealt with separately.
The first is the maps data. Apple has a some huge issues here, especially around towns missing, streets missing, and POI's missing. That's all fixable on the server side - they just need to get the data and ingest it.
The other issue - it's not an issue, it's just a discussion point - is the app itself. And it's not getting much talk because of the data issues.
The app itself is lovely. Plain and simple, it's excellent.
The maps are fast and smooth. You can zoom in and out very quickly without taking a huge bandwidth hit. While they have a different look to the Google tile set, they are attractive, easy to read and helpful. If you turn on small labels, it's even better.
And that's while only considering the upgrades to the existing functions - the new turn by turn directions, 3D view (which is actually quite useful!), and other features are great in and of themselves.
I just wish people could upgrade, and if it is a big issue in their area, downgrade again. I guess if a Google Maps app comes out, they effectively can.
So, if Apple can sort out the data issues, this maps app will be orders of magnitude better than the old one. I'm confident they will, as it's one of the few things that having an obscene cash balance CAN solve.
--  I'm 100% positive it's a LOT more work than that. But I'm not a geo-spatial engineer :)