I ended up getting one of those ear bone conducting mics, too. My audio report this morning with the VX-7R was muffled audio, readable but muffled. The comparison was that it sounds similar to the built-in mic on the VX-7R with the membrane still on.
The earphone sound is thin and tinny, but that's to be expected as well. Not really any worse than the internal speaker, which I've always found to be very poor at anything higher than ambient room volume. It allows a lower volume with more background noise, the ear plug does a good job at blocking out other sounds (almost too good, I only hear ambient noise with my other ear).
I do not get feedback and the PTT works fine. Not too bad for $19, but it's not super high fidelity.