The Model S is not 100% like an iPad, sure it has pinch zoom etc but the responsiveness sometimes is spotty. The graphics and google maps are pretty cool. Being able to see the traffic is awesome. There are claims of apps being available but there has not been a single third party app developed.
Semi OT question: On the Karma if you have a paired iPhone can you push the "Talk" button on the steering wheel and ping Siri? You can't do this on the Model S as yet. I find the intelligence of my phone to be far superior to the Model S or any car that I have owned.
I like the haptic feedback of the Karma command center. Sure it is a bit slow but it looks cool in retro sort of way. IMO the Karma's cluster looks better than the Model S' cluster. 10-15 years from now, I think you will look back at both of these cars and see one vehicle has aged well and still looks good and the other one looks severely dated (both inside and out).