This unit’s main benefit to me is letting me listen to satnav instructions in-ear either whilst driving(so the other occupants of my car don’t have to put up with it!) or when out riding on my pushbike.
I also use it to listen to streamed talk radio late at night in bed, when only needing one ear and having no wires to wrestle with are practical boons.
As a calling device however the MBH20 is actually a downgrade from previous models Sony have produced, such as the VH300. The lack of support for voice-controlled dialling is a major limitation, particularly in the car. Maximum in-ear volume is certainly lower. A curious development really. The MBH20’s form factor is great, but if only it had the VH300’s functionality and better sound, it’d be a real winner for me!