In real life we are not soaring above the map and looking down from a 45 degree angle. Well, not most of us.
Call me old fashioned, but I think a map should look like a map. The less clutter and distraction the more likely I am to find what I need and how to get there. Then again I still use actual maps (remember the kind that came on paper?) from time to time so maybe I'm jaded from so many terrible experiences with a GPS.
Honestly if someone, anyone, created a GPS, be it an app or a stand alone unit, that actually worked, updated easily, didn't intentionally make you go crazy routes and waste gas, I would rejoice. The idea of GPS in your car/on your phone has been around a while now and no one has gotten it right yet. Don't get me wrong, there are some cool programs, but none of them do it all well.
Paper maps are never going to catch on, because in real life we're not looking at roads from above, and the real world is not made of paper.
I don't expect everyone to do their turn-by-turn navigation in full rendered 3D mode. Both Apple and Google's solutions will have options to use more traditional "flat" maps. The 3D options make the maps useful in ways that 2D maps are not, such as getting a good idea what your destination actually looks like. A flat map of a city is very misleading, especially if the city is one as non-flat as San Francisco.
The 3D options make maps more useful to me. If they aren't useful to you, you don't have to use them.
If it annoys you that the maps have an optional feature like photorealistic 3D, that's just a bonus for me.