These are 7 years old, some will have serious battery issues. My first from ebay was DOA, vendor shipped another right out. Second one charged, but I couldn't get it to pair, checked Plantronics support and the incl instructions were wrong, had to hold down power and mute at the same time to initiate pairing mode. Worked fine.
So far paired it no issue with Android phone, Samsung Galaxy light, and it does music incl skipping tracks. Sound seemed fine to me, and yes it works with my mono headset fine. Mic is in the headset portion, not the pendant.
More to test, but its been kind of busy.
Old battery could explain a lot of the complaints. Looks like the battery is a generic Lipoly sold by its dimensions, 403020 or 402030 something like that, about $5 on ebay from China, so I may try to revive the DOA unit.
I'll post more once I have more play time.
High quality sound may require something supporting aptx. Wired much cheaper option if you can go wired.