I abhore the earpiece that comes with my phone/MP3 player/whatever-else-it-does and refuse to have it anywhere near my ear. Plus, I don't think I'd get more than 50 yards without the piece of crap falling out or being uncomfortable and needing adjusting 
Having said that, I wouldn't want my hearing ability compromised at all while I'm cycling, as for me, it is an extremely important sense. So I see no reason in investing in a better earpiece anyway.
Whilst driving, yes, the radio is on, although never so loud that I couldn't hear a horn blast if I needed to.

Having said that, I wouldn't want my hearing ability compromised at all while I'm cycling, as for me, it is an extremely important sense. So I see no reason in investing in a better earpiece anyway.
Whilst driving, yes, the radio is on, although never so loud that I couldn't hear a horn blast if I needed to.