"Person you talk to can't hear you; lots of static on their end"2.0 starson by Jennifer1822
Pros: comfortable, lightweight, fit well in my smaller ear, I could hear well usually
Cons: the person you talk to hears lots of static; if you move away from your phone more than 5 feet you get static in your earpiece
Summary: I bought this 655 as a replacement for my 645 which got stepped on by someone. I loved the 645 but thought I'd try the "upgraded" model for the same price (thru Newegg).
While it was comfortable, I have used it for a week and no one can hear me talking. Everyone I have talked to this week has complained that all they hear is static or nothing at all. There has also been a lot of background noise and wind affecting it even when I'm just in a relatively quite place like Target. Also, while mostly I could hear well it would have static and cut out on me from time to time. It doesn't have the range that the 645 had.
My husband was so frustrated from trying to talk to me this past week we decided to return it and get my old 645 again, which I have loved and never had any problems with people telling me they couldn't hear me (I had it for 6 months). Also, like other users there is no good case for all the extra pieces, and of course you don't get as many chargers. For those looking to replace the 640 I would highly recommend the 645 over the 655. The 645 seems to have fixed many of the problems the 640 had, while the 655 just got new problems.