From the sounds of your statement, I don't think you have used beta4 extensively. The 3D buildings in vector already makes it better than navigon and I can sort of see how you think it's beta-ish because it's pretty baron when it comes to on screen POI icons, etc. However, I don't care for those things because navigon can be really clusterfxked with the icons on screen. Biggest thing is that with apple's navi, it is incredibly smooth - compared to navigon side by side, navigon is quite stuttery. The re-routing is extremely fast on apple's navi.
When you travel on your route, the screen will pan, tilt very smoothly - navigon does the same thing but it's ultra ugly when it does. Like I said, I am still using navigon since I can't use up all of my data for my iPad. The offlinemaps have apple beat, however.
If I am to recommend a 3rd party navigation, I wouldn't hesistate to recommend navigon - but when the final ios 6 unveils to the public, it's gonna be a huge dent in sales for any 3rd part navigation software.