I can't speak for them, but, around me, almost all addresses are off by a good amount, detail is lacking in all the maps, and there are minimal POI listed.
I'm sure the experience is different for all of us.
I on the other hand have had great success. Every location I search (family, friends, favorites restaurants, favorite places I visit all from various cities) have been very accurate.
I even search Mexican restaurants, sandwich shops, etc... it is giving me more results than Google Maps does (my brother still has his 2nd generation iPod touch) and for my location the satellite view is more up to date than Google was.
I've also used the Turn-by-Turn navigation 9 times now and it has gotten me to my destination just fine.