I have installed the Google maps app on my N95. My quick impressions (and why I won't be using it):
Pros: Fast Smooth operation Easy Interface, the menus make sense
Cons: Does not have an option for keeping the backlight on Does not go into much detail for places like South Africa (unlike the Nokia maps, which seem to have the whole worlds road marked)
The pros would easily outweigh the cons, if only I didn't live (far) away from the mainstream like I, and most of the world, do.