+1 while I may have my phone connected I avoid making calls unless stuck in traffic and not moving. If I receive a call, then I will still tell them I am driving and I will call them back when I am free.
No matter what people say, when you are on a call or even fumbling with the voice or menu options to read the texts you are not focused.
You used to have full text integration in the previous generation of the onboard systems in the UK, but it was removed as it was seen as unsafe. At least in this one you are only read and not send (or have Mavis Beacon read it to you in a funny way)