Looks like there is a new personal navigation app for iphone and it looks pretty impressive so far. 70 bucks is quite a bit but if it can follow through on some promises it makes it might be worth it.
http://gizmodo.com/5320284/navigon-m...ore-70-for-now
EDIT: They also have a free lite version you can try...although at the time of this posting, the app store wouldn't let me download it. It's called MobileNavigator.