I haven't tried the new Galaxy Tab yet - although I did root my Nook Color recently and just use it as my bed side internet browser, Nook/Kindle reader, Facebook appliance, and Gmail reader.

I'm not sure how the Galaxy compares, but I'm not impressed w/ Android 2.x on tablets. I'm waiting for the new Honeycomb version to come out.

I'd love to see how yours setup turns out. I've done the CarPC route before in my BMW E46 awhile back. With our cellphones/tablets being more capable these days, it's a great idea.