Its a great free service but it has a lot of minor issues. I'll name a few to show you guys what I mean.
For example, try entering this address:
2486 NC HWY 904
Fairmont, NC 28340
It won't find anything at all. After messing around with it for a long time, trying different combinations, I found out I had to input the address displayed below to get it to detect the location:
2486 N Carolina 904
Fairmont, NC 28340
Now most modern GPS devices don't have issues with ancronyms like HWY instead of highway, or NC instead of "N Carolina".
The VZ Navigator I had on my old phone didn't have that kind of problem. I also think it would get more accurate results if it had individual boxes for zip, city, road etc...
It might not seem like a big problem for most people, but when you type in an address just like its listed on incoming mail to people's houses and it doesn't detect it correctly, its frustrating.
Another thing it is missing that I liked from VZ Navigator was the ability to change how it calculated routes (based on time/speed limits, or by miles, or few turns etc...). It also doesn't have an option to avoid HOV lanes (a lane where you need multiple people in your car to legally drive on that lane...some places have those for you country people).
The MAP data is not as mature/detailed as other popular GPS systems. Every GPS I have ever seen has always had some errors or didn't have every road listed, but it seems like a more common issue with Google's GPS system.
However, it does keep a connection very well, at least on the DROID with Verizon. If you are lost, it might not take you the best possible route, but it will get you where you want to go, with no hassle.
It does sport some "kool factor/geek" features like the satellite imagery, 360 degree street view and such. But its missing some of the "more productive/useful" features, like I described above.
I think the best thing about Google Navigation is that it's on my phone. I carry my phone anywhere I go, and so I always have it with me. I couldn't imagine walking around with a TomTom in my pocket, lol! However, if you plan on using it for more than an hour in a single day, you really need to charge it or it will drain your battery quick.
Another awesome tip is to use it to lookup nearby restaurants and it will list the number to call them. You can use that to order ahead of time and pickup your food when you get there (or avoid waiting in line). It beats looking at the refrigerator hoping you have a number for the place written somewhere, such as when you want to order Pizza!
Overall I love it and I wouldn't dare buy any GPS software over using this free and fun service.