I don't mind the two touch screens in my car, but I too like buttons for the most used buttons. I feel like I have the best of both worlds because the AC/Heat still have buttons and there is a volume knob. I really don't use the volume knob often because the steering wheel controls are more convenient.
I will say, I tried to go the whole iPad as a remote for my Home Theater. Worst decision ever. It's freaking horrible! Not having physical buttons on a "remote", in the dark, sucks. You have to turn on the screen and look at it. I gave that up real quick and moved on to URC remotes. They are amazing if you have the software to program them. They won't give it out the software and want you to use an installer, screw that, I can program my own remote and save a thousand dollars to have someone program my dang remote. The software isn't too hard to find though.