Glad there is still some interest in this. There was an article on here a while back where a respected forum member had voiced his opinion that tablets were going to replace CarPCs.
I believe he is right. It's a sad fact that I can get a phone now with a 720p resolution OLED screen and capacitive touch for under $200 (on contract of course), yet the best I can get to build a car PC is 480p, TFT and resistive touch. If you want to see it in sunlight (which I do) then it is going to cost over $600 just for the screen.
The BOM (bill of materials) is so cost prohibitive, I've never been able to commit.
The manufacturers are making baby steps. Sony finally released this Christmas a single DIN unit with Pandora support through a bluetooth connection on either an iPhone or Android device. Obviously, no maps, trapster, or anything else that makes a car pc useful, but it's the first of its kind. Pioneer also released it's second generation AppRadio device, which actually has a full 7" cap touch display. Although only 480p, it is a decent price at $500 street. The Achilles heel of the device though is it still is going to require a physical wire connection. Plugging your phone in is an amazing nuisance.
I finally bought an android phone and data plan, but before committing on a new head unit, I just ran a stereo jack out from the aux in to plug my phone in. This works, but it is enough of an inconvenience that I will only do it for long trips. Also, I've discovered the new Pioneer unit will connect to Android devices via the HDMI jack. The phone I bought doesn't have one, since I didn't think I would ever need to hook my phone to a TV.
I think a well made android head unit would sell very well, but the time it would take to develop is in the 10's of thousands of man hours. I would need to quit my job and convince a bunch of other people as well, and with mortgages and car payments, it makes it a very tough sell.