I think it's very interesting what you are doing. I've been using Pandora on my phone a lot lately, but only at the office when on WiFi. I haven't hooked it into the car, but I should try it to see what kind of reception I get while driving around. Simplify Media will definitely be on my list of things to tinker with this weekend, as it sounds like it is working well.

Overall, I think this is the future, and it's not that far off. With wide area networks (3G and other cellular data services are basically a WAN) continuing to advance along with the portability of devices, I think even flash memory is doomed for storage in everything. Why bother keeping 4 copies of your data in various places (desktop, phone, laptop, car) when you can just pull the data over your WAN connection instantly?

For now, it might be a rocky start as the data providers pull back that "unlimited" tag, but all it will take is one provider to do it right to force change. With every generation jump, there is always the chance for someone else to come along and do it well. 3G is here now, time to look forward to 4G.