I would really love to see some caching done on maps – if just the 2 miles around my house were cached, I’m not sure I’d use a quarter of the data I currently use. Downloading music would also be nice as the GSM network in Westchester NY is kind of a joke. A Google Play All Access type of model would be nice – something where I could download a library from the web (or even my home NAS!) and have it stored locally. Currently about half of my listening on Slacker is filled with skips and starts due to poor network connectivity.
As for other features, I’m assuming Tesla will stay away from video on the big screen but it would be nice if they hooked up with Audible for books on tape or other news orgs (NPR?) for audio feeds and podcasts.