First, the good news. The unit is light as a feather. Controls are accessible and well laid out. It fits comfortably under my bike helmet. Sound is acceptable. Syncs up nicely with multiple devices (iPod and Cell Phone).The Bad news:The first unit I received was DOA.Returned it and ordered another one directly from Motorola.Received the replacement unit and charged it up for two hours. Got the steady green light indicating good charge. Jumped on my mountain bike and headed up the hill listening to tunes from my iPod playing nicely via 10-Tech Naviplay bluetooth transmitter.Unfortunately, the S9 only lasted only 4 hours before the battery died.When I got back home I plugged the unit in for charging and left for the afternoon/evening. Returned 8 hours later. Unit is dead. No lights, no sound, no activity. Kapudt.There definately appears to be a problem with the S9's charging mechanism.The service person I spoke was not familiar with the S9. He said I probably "overcharged" it by leaving it plugged in too long.Overcharged it? Are we supposed to stand there with a stopwatch for two hours? That's rediculous. We can leave our cell phones, iPods, and other devices on their chargers for weeks with no problem. Something is not right with the S9.Sending it back to Motorola for replacement. Maybe 3rd time will be the charm.