I think Apple will continue to improve.
In my area (Columbus, OH), the maps are pretty good, with what seems to be a good number of POIs and such. I used it to navigate home from work (just to test it out) yesterday, and while I think I'll stick to Navigon or MotionX for longer trips (just because of their feature sets), I did notice some very nice things about the turn by turn with Apple maps.
1) If you are navigating and open another app, such as a radio app or something...I like the fact there's a green bar to quickly return to navigation, and that it uses that bar as a banner space to give you an upcoming turn. This is really handy, and is something the other mapping programs can't do on iOS...you won't miss a turn if you have the voice turned off and enjoy looking at album art or something.
2) Similarly, if you have your navigation on and you lock your phone because you don't need to see 100 miles of highway map on your screen, the maps will show on your lockscreen along with your next turn. This too is REALLY nice...it'll also briefly wake up your phone (without unlocking it) to show you when a turn is upcoming. Saves battery on the backlight and still wont cause you to miss turns. And you can just click the home button if you want to see your current status on the trip, rather than unlocking the phone and going to the app.
3) While the in-map controls are pretty sparse, you can ask Siri about points of interest along your route. This still needs a little work, as Siri should really concentrate only on POIs that are FORWARD in your route, but if I asked "are there any gas stations along my route", siri brought up a list of gas stations along the route (or within 1 mile of the route) and showed me where on the map to the nearest one. They need to allow this to add that POI as a mid-route stop, though..now if you want directions to it, you need to change your navigation to the POI. ...maybe in a future update.