The only problem I have found is that the unit goes into a sort of sleep mode when you're not gabbing and on my system (Quest & BTA II) when the Garmin tries to give you the first of the route messages, you miss the first bit, maybe as much or as little as half the first word. When it repeats the message as it counts down to the turn it's okay.
In the old days of the Sonic bike to bike system to switch on the VOX you had to sort of make a noise then speak! Just a little rasberry to get it on then it was okay.... strange but true!
As for hurting the ears, the speakers are wafer thin and even on the C2 (on the few times I had it working) there was just enough room to fit it without fecking about with hot knives and dremels to munch away the polystyrene inner helmet. adsly, the C2's lining it impervious to velcro and the thicker toothes stuff on the back of the Scala's speaker so the bastards fall out easily. No such problems in a Nitro or the piss cheap bucket I used for the first test from Caberg.