The GO 300 has a built-in Bluetooth connection that allows you to connect your mobile phone to access TomTom PLUS services, i.e. Real time traffic, weather and extra downloads such as detailed city maps, additional voices and points of interest (POIs). New customers receive a one month free trial of TomTom PLUS services. I was not able to test this service because it doesn't work with my Treo 650 mobile phone.
Mac compatibility. The TomTom GPS units are Mac compatible, which means that adding features or software updates can be done from a Mac instead of having to find a PC or boot into your XP partition of Boot Camp. TomTom Setup 1.0.4 allows you to install maps, voices and the application on your TomTom GO device from any Mac running Mac OS X 10.3 or later.
It runs on batteries. Unplugging it from your cars power port, say to charge your phone, allows it to keep running and bringing it into the house to enter destinations doesn't require that you stay tethered to an electrical outlet.
All the map information is stored on a removable SD card which means that you can easily change maps for, say different countries by simply switching SD cards.
A nice feature is the GO 300's ability to select a crossing street when inputting a destination. Some time you don't have an exact street address and this is a an easy way to find your destination.
Screen glare is an issue with the GO 300, it can be difficult to read in bright daylight, especially on sunny days if there are bright objects in your vehicle or if you're wearing a bright shirt.
Entering a city should use proximity, for example I was recently searching for Springfield, PA and I had to scroll through a list of every Springfield in the U.S. And yes, there is a Springfield in every state in the union.
The suction cup windshield attachment takes a little finagling to get right. If its wrong it will fall off and take out your knee.
No light sensor so it doesn't auto-dim the display at night time. The brightly lit screen can be a little distracting, switching to night mode isn't difficult, it just requires a couple of clicks into preferences to change.
The GO 300 has a 2.5-inch (diagonal) display and the buttons can be a little small if you have large fingers. I find is especially hard to accurately click on the UP and DOWN arrows and frequently clicked on the wrong destination.
A really fun feature of the GO 300 are TomTom voices. Instead of being navigated by a dry, computer-generated voice you can purchase different options like the hillarious John Cleese, or the sexy Sylvia (who "will help you reach your destination, guaranteed!").
Although it has some minuses, many of the issues above are addressed in higher level TomTom models like the GO 510 and 910. Overall, the TomTom GO 300 is a great way to get into the GPS game without spending four figures on a receiver. When you add to that nice plus features like traffic and weather and built-in Mac compatibility you have a nice little GPS solution that won't break the bank.