I'm actually torn about Beagleboard xm vs igep vs sheeva vs something else.
Here are the devices I need/want to be able to access:
1) Need: Spinning rusty metal media [flash burns out easily with an application like mine]
2) Need: OBDII
3) Need: GPS
4) Want: Smart power supply that computer can talk to [eg the dcdc-usb]
5) Want: Character/graphical display
6) Want: Space for hypothetical future stuff
Obviously there's at least one more thing listed than usb ports on the beagleboard. I have bluetooth OBDII and GPS devices, but obviously they both come with other problems [batteries suck. my bluetooth gps device takes a long time to get a good lock].
The SheevaPlugv3 [which is nearing a year since its announcement and there's no hardware to buy yet] had an internal hard drive, which would have been ideal. An eSATA port or similar instead of a USB port would also be great.
Perhaps the guruplug server plus is what I want, although then the downside is no "real" graphics port. eSATA is awesome until you go trying to figure out how much it'll cost and how you'll power it in your car.
In my dreams, a device has the OBDII device internal - something like the microOBD attached to the UART on the igep, where two purposes are served: It doesn't use up a USB port or similar, and [more importantly] the device is only powered when the computer is on. I spent years parking my car on a sloped surface so I'd always be able to bump start it if needs be, and let me tell you; that sucked.