I have an HTC Thunderbolt (Verizon/Android). The phone connects correctly with HFL and everything worked except for the volume. I had to turn up the volume to level 15/16 to hear. The problem is that the HFL commands were then very loud. Then occassionaly the volume level would be even worse and even at level 20+ the call volume was low. This would happen somewhat randomly, but about 25% of the time.
Just recently, got an update to the OS that was downloaded and installed automatically. Volume Fixed!

Now I am at Level 9 or 10 and it is perfectly clear.