I've had this headset for quite a while, and but for one issue it works great. When I purchased it this headset was the most inexpensive single ear headset with A2DB. This means it is compatible with VoiceOver as well as playing music, audio books, podcasts, Etc. There is an actual power switch so there is no doubt whether the headset is turned on or off. The volume is loud enough in every situation except when at a busy street corner. The people I have talked to say they can't tell I'm on a Bluetooth headset which I think is as good as I can ask for. The headset is tiny and has a non-replaceable battery. It charges via micro USB in about an hour and the charge lasts at least a day of continuous listening and several days on stand by. A handy feature is that the battery status of the headset shows up on the status bar of my phone next to the phone's battery indicator.
My only issue with the M50 is you cannot Play, pause, rewind, or fast forward the currently playing audio from the headset. The headset has a button which can be used to answer calls and activate siri, but it can't do anything else unfortunately. Even with this annoyance for the low price this is an excellent headset.