The Navigon 2100 GPS, although purchased refurbished, was far more than what I had expected.
As a test, I took a recent trip to Rhode Island, roughly a 2 1/2 hour drive from my home. I powered on the unit, and immediately realized that the GPS was quite accurate, and although there is no view of how many geosynchronous satelittes you are connected to, I only had a period of about 3 minutes where the unit went into "simulation mode". Simulation mode is when the reciever cannot detect a signal, and uses the information that it already has to determine where you should be at a certain point in time.
Some of the features on this unit that impressed me were the speed limits on the roadways. The unit comes pre-programmed not only with maps of roads and common destinations, but also the speed limits of every road. The unit realtime calculates your speed and then warns you if you are exceeding by an amount you specify. Along with realtime calculating speed, it also calculates your approximate arrival time, which was quite accurate, I was 2 minutes earlier then what it had estimated initially.
Now for the cons, the screen, although a very high quality screen, gets fingerprints on it very easily, so you will want to keep some screen wipes handy. Also, even at max volume the audio often gets drowned out by the sound of even the quitest radio.
Although these problems can be a nuisence, they would not have prevented me from purchasing this unit even had I known of them.