I have Navigon for North American and Western Europe. I am in the Netherlands right now and I find that for some reason, Navigon is flakey in my rental car. This is on both an iPad and an iPhone 3G. Maybe my car has some sort of window covering in the glass that blocks GPS signals.
There are two huge, almost showstopping problems with Navigon (for me):
1. It is unusably slow on an iPhone 3G with iOS 4. You won't even be able to use it, literally. I've waited half an hour for it to start giving me navigation before giving up and turning it off.
2. If the signal isn't PERFECT, Navigon will stop giving directions. I'll get an error stating that Navigon can only get a GPS fix within 5 metres, and it will stop giving navigation. It will just sit there at the point of last fix. W. T. F. If you know where I am within 5 metres, you know where I am! This makes the app completely, absolutely useless in a car where you can't get a good fix. I don't have this at home with either of my vehicles but here it made Navigon useless.
The other day I obtained TomTom as we have a couple thousand km to drive and need the navigation. When TomTom can't get a perfect fix, it lets you know but it keeps on giving you directions to the best of its abilities. I think the money I spent on Navigon Europe was a waste.
Navigon has some nice features, like the ability to use the scenic route. I rarely find that I lose much time on the scenic route, and sometimes it's even faster.
Navigon also won't navigate from the Netherlands to Switzerland in one go (~800km) whereas TomTom will.
Navigon's latest update completely sucks on the iPad. They screwed up their icons or lists or something and they are all the wrong size, or blanked out unless you scroll down and back up again.
Navigon provides no way of giving feedback, other than map errors. IMHO this is unacceptable. Refusing to listen to paying customers shows an arrogance that makes me not want to support that product in the future. I don't know about TomTom as I haven't tried to provide feedback.
Okay. You're wrong. The 3G does have a GPS receiver. (Infineon I think) Yes, it is A-GPS, which just means it's GPS with the benefit of a faster startup time thanks to the data connection.
You're right that the 3G does have a GPS receiver, but the 3G A-GPS is more than that.
Using a combination of cell tower triangulation, wifi location and actual GPS, the iPhone narrows down your location as quickly as it receives any of the above 3 pieces of data. This is usually why you'll see the giant circle that gets narrowed down as the GPS receiver gets an actual coordinate from the satellite.