I hated using a touchscreen navigation system in a previous car. The loss of tactile feedback is nothing to sneeze over, as I much prefer even a rotating dial interface which I can use while completely visually (not cognitively of course) focused on the road. This increases at least perceived safety by a large margin. An ideal combination might be a touchscreen with tactile feedback buttons, which I think has been used to limited success before. Or just voice or alternative input...