I currently am having a blast with my Eee. I made a mount for the truck and am using a 353 puck for GPS duty. Its a bit frustrating using the touch pad but I am not playing with it when driving anyways. I have the stereo output of the laptop hooked into the auxiliary of the stereo. Works great for a temporary setup.
My end goal is when the Eee 2 or equivalent comes out with a 9" screen I will pick it up and this one gets chopped up to be put in the dash with a touchscreen overlay. Simple and effective.
Its running on a nlited xp, no pagefile and 2gb ram and I couldn't be happier with its performance. Loaded with everything I want its about a 20 second start up. I've had it much faster but ran into assorted issues not having all the components I needed to run everything I wanted (I am a nlite noob) so I was generous on this nlited disc. Ended up with a 500mb install.
Edit: I just ordered a Eee touch screen kit out of Hong Kong for it. What the heck... It willl still be in laptop form but will be one more step towards a carpc...