I have the Garmin 665. It has a few annoyances, but seems to be reliable, pretty easy to use and seems to work well with gloves. One gripe is having to remove the battery door to plug in the USB and the GPS doesn't function with the door off. It seems like a minor thing, but tends to be more of an annoyance than you think it would. My biggest disappointment is the stereo bluetooth (one of the reasons I bought a higher end model). It syncs up fine with my Sena SMH10 and my phone, but the music clips; particularly on the highs like cymbals (some songs are way worse than others). Do some searches and you'll find a lot of people have that problem with it (the ear phone plug sounds fine). I can't comment on the bluetooth stereo of other models. Long story short, I still use my phone for music. The 660 is the same as the 665 except that it doesn't support XM radio and weather. For GPS everyone I know that has the 550 loves it, but the bluetooth is mono and it's getting a bit dated...especially considering they still want as much for it as the 660. The 550 also has less memory so you may only be able to load a portion of a planned trip at one time. All in all, I like my 665, but for the price I'm more than a little disappointed with the bluetooth performance.
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