Are Satellite Navigation Systems Reliable?

Satellite navigation systems have become extremely popular over the past couple of years. They used to be things which only few could afford but these days it seems that most people have one fitted into their cars.
Generally the satellite navigation system receives a signal and it shows you exactly where you are. You need to tell it where you want to go and it will work out the quickest route and tell you exactly where to turn etc through voice software. They are really clever but many people have reported problems with them. For example, some say that their systems have told them to go through rivers, some have crashed because of their satellite navigation systems and others have been told to do u-turns on motorways. So, there does seem to be an error somewhere but generally satellite navigation systems are fairly reliable. You just have to ensure that you purchase a good brand so shop around to find the best one for you.