For folks who are purchasing premium slacker subscriptions (or thinking about it) you might consider that Tesla might offer them bundled with whatever future data plan they will offer. It might make sense for some people to buy a Slacker subscription anyway, and use it for their car as well as away from the car, but for me I'm holding off on a premium subscription until 1) the car allows me to use all the features of a premium subscription and/or 2) Tesla announces their data plan and pricing (and if it does, or does not include the subscription).
I do have a basic subscription to slacker, and I'm hoping that the car will eventually work with that as well. I guess I'm just throwing out a word of caution before people invest in the premium subscription.