While driving I keep my phone sitting in a holder on my dash, and while the Pre's speakerphone works well in the car, you can't answer the phone directly with it. Instead, you have to answer the call, wait for the phone app to pop up and eventually click the speaker phone icon. This is slow and does not work well while driving.

Instead the phone really needs a means to answer the call immediately to the speaker phone. It shouldn't be the default, but it should be easy to do.