I spent a lot of time trying out GPS units, and have compared Garmin, Tom Tom, Magellan, and several factory GPS units. All of these GPS units tell you how to get somewhere and will re-route if you make a wrong turn. However, Garmin is my absolute favorite, and here's why:

1. The most important thing about Garmin units is the user interface. It is simple to understand and easy to use.

2. The Garmin unit uses a built in database of sunrise and sunset times (based upon your location) to automatically change from daylight mode to night-time mode. This is important because the daylight screen is much too bright for use at night. With the Tom Tom, you must make this change manually.

3. If you have the Garmin unit plugged into your car power, when you turn off the car (and the cigarette lighter power goes off), the Garmin unit will detect that and automatically turn itself off (it gives you 30 seconds to override and keep the unit on).

4. When you start your car again, the Garmin unit will detect that too and automatically power up. If you were in the middle of a trip, the Garmin unit will pick up where you left off, and you won't have to tell it where you were going again.

5. Unlike most factory GPS units, Garmin will allow you to select your route and make changes while you are moving.

6. The Garmin units have an extensive database of locations and the excellent interface makes it easy to search the database to find what you want. Do you want food or gas? Just click three buttons and a list of locations (sorted by distance) will appear. If you know the name of the place you want, you can type it in on the on-screen keypad and Garmin will find it for you. You can even add your own locations using the favorites feature. I first started using this when I was out of town, but its amazing what you'll find near you when you look.

7. While you are driving, the Garmin unit will both prompt you to turn and give you a written explanation of the turn (including the street or highway name and direction) at the top of the screen. The Garmin unit also shows an estimated arrival time (usually a few minutes earlier than you'll actually arrive) and the distance to your next turn. A separate screen gives you detailed trip information, including how far and how long you've been driving and your maximum speed. I used mine on an airplane once (yes, it is allowed - read the back of the airplane magazine), and it now says that by maximum speed was 590 miles per hour.

8. I often use the Garmin even when driving locally, becase it often finds better, faster ways to get there then the way that I usually use.

9. Garmin offers a variety of installation options and accessories. My favorite is the friction based dashboard mount (three weights connected to a center stand) which is much more convenient than the supplied mounting system.

10. If you turn off the GPS receiver (see settings) and then look up another location, you will get the option to set this new location as your present location. This will allow you to use search Garmin's points of interest for the new location. This is a great feature when planning trips, because Garmin's points of interest database is quite extensive and includes all of the typical tourist attractions, plus food, shopping, gas, banking, etc.

11. Be sure to check for the latest map and firmware updates at Garmin's web-site.