I bought this for use with a Treo 650.It took a couple of tries to get the two devices to play nicely together.The instruction manual is particularly hard to follow. Each page has a cryptic drawing followed by a single sentence in about ten languages, followed by another cryptic drawing, etc. The buttons are very small and can be difficult to operate precisely even for someone with small hands.The battery does not hold a charge for anywhere near the hours it is supposed to on standby.I have fairly small ears close to my head, and the headset always feels like it is about to fall off. Sometimes it actually has fallen off.The rubber gizmo that is supposed to rest inside the ear comes detached *very* easily. The unit ships with two spare gizmos, which may not last me a month.Sound quality is okay but all in all this is a long run for a short slide. Plantronics usually makes better products than this.