We were given these phones as a christmas present. Although all the set up process was easy, the phone call quality IS awful. There is constant line hum from the internal psu and the volume level of the callers as very quiet. The sensitivity of the mic is very poor also. Whenever I make calls using this phone, the person/people at the receivng end are always asking me to repeat what I say.
Being an openreach enginee, I decided to test my telephone line. Using a series of stadard techniques, I located the noise and poor quality to these handsets.
In short. I would steer well clear of these.

Superb. Will suit hearing impaired phone users because BT has a wider frequency range. For profoundly deaf the texting facility enables communication with others.
Excellent clarity, considerable range of controls re volume, ringtime, ringtones. Auto transfer of date and time. Massive memory with shortcut find for stored numbers.
Only one input of data required - one button transfer to each of multiple handsets. Ample message recording time for me.
Even the main base phone cordless - marvellous. The satellite phones only need the charger plugged in - so many wires eliminated! It's exhausted our needs but not the capability of the system - which is said to be expandable if you want.
Excellent handbook and instructions.