The c550 is a major improvement over Garmin's first warm-and-fuzzy navigator, the c330. Last year, I said that while I enjoyed the c330's extremely friendly interface, its screen was too hard to see in sunlight. Other c330 flaws included a windshield suction cup that just didn't suck enough, and a GPS chip that would lose reception when driving on an underpass. In the c550, all three of those mistakes have been rectified the anti-glare screen is much easier to see under the hot summer sun, the suction mount holds fast to the windshield, and a new GPS chipfrom a specialized manufacturer called SiRFcan pick up satellite signals even when you are indoors.
Those major improvements would have been enough for me, but the c550 has additional functions that make it roadworthier still. Its lighter-jack power cable doubles as an antenna which receives traffic updates that the mapping software can use to plan routes. The information itself is provided by Clear Channel and you can check if your hometown is covered at realtimetraffic.net. While I haven't yet found it to be very useful, I believe that it's a good thing to have on hand as Clear Channel's reporting system evolves.
The c550's built-in Bluetooth means that if you have a cell phone that supports wireless hands-free devices (and more and more of us do these days), you can use the c550 as a speakerphone. From a few feet away, it does an admirable job of picking up your voice, and its speakers don't mangle the voice of the person on the other end like some speakerphones do.
There's also a music player that will read MP3 files that you put on an SD card. While it's not an iPod (and won't support music you buy at iTunes), it is a handy player, one that works in conjunction with the speakerphone and turn-by-turn navigation, muting when you need to hear something more important. You can even plug the c550 into your car's stereo using a tape adapter or FM transmitter (both sold separately).
My only wish is that there was a way to plug an iPod directly into the c550, so that you can play your music through it, and still hear the turn commands and phone calls. My sources indicate that something like this is being researched, but in the meantime, I can safely say that after all of the testing, we have a winner.