A touchscreen can be made very user-friendly;

Use the four corners and middle for five buttons. If the screen is large enough, then adding 4 tactile dots on the surrounding bevel at the center of the edges would allow a further 4 buttons at the middle of the edges. Use a beep to replace the tactile feedback that buttons would normally give. Make sure that the touchscreen has a (configurable) delay so that the first touch can be used to 'gain bearing' on the screen. If possible, make a couple of (tactile) thumb index positions at the bottom left and right of the unit, so that the user can place their thumb there and 'learn' the screen position. This is especially useful in the car where bumps and jolts would otherwise move the hand.

Touchscreens can be done well, but it's rare that they are!