A good portable GPS device is like a good passenger on a road trip: helpful, not too annoying, and low maintenance. The Navigon 2100 Max succeeds at the first two: It will get you to your destination without overloading you with superfluous information. Unfortunately, in my tests the unit was a bit sluggish and its interface wasn’t always intuitive.The $299 2100 Max is an upgrade of Navigon's $200 entry-level 2100 GPS unit, which the company launched last year. It sports a sleek, thin design and a 4.3-inch wide screen in place of the original device's 3.5-inch screen. It ships with a 1GB SD Card preloaded with Navigon's maps and a fairly comprehensive points-of-interest database.Once you begin navigating, the 2100 Max provides sensible directions and alerts you to impending turns well in advance. It reroutes you when necessary, without making a federal case out of the altered route. On some occasions when I was rerouted, however, I noticed sluggishness; once, for example, the 2100 Max had me sitting in a parking lot wondering which way to turn while it caught up.A bigger issue is the device's usability. Entering information on the touch screen can be difficult, as some of the buttons are too close to the edge of the device and in some instances fail to register taps. At times the touch screeen acknowledged my taps but didn't react to them until after I had already tried again, so I ended up entering info twice. Still, the device's home screen is nicely laid out, presenting you with four options: New Destination, My Destinations, Take Me Home, and Show Map. When you touch New Destination, you have the choice of entering an address or searching for a point of interest (POI). The POI database is impressive, listing a number of locations even in my relatively small town. If you enter an address, you can input the street first or the city first--but neither option works in a sensible way. Both alternatives require you to enter the street name before the address numbe...