I too saw those complaints before buying mine, but I decided to take my chances.

My partner, who is about as good at evaluating these things as I am after 20 years running sound, says that my transmit audio, both phone and DC, lacks a bit of treble, but is otherwise as clear as you'd expect from a properly functioning digital codec, and my opinion of the receive audio is similar, on both the high and low speakers.

Is it perfect? No. Could it stand to be a bit louder? Can't it always? :-)

But is it serviceable?

Certainly it is.