I use my sony laptop in my van for navigation among other things. I have it hooked up to a 7" xenarc touchscreen that i have mounted on my dash. This allows me to keep the laptop screen closed most of the time which helps with keeping some dust off of it. I also replaced the hard drive with an ssd hard drive so no need to worry about vibrations killing my hard drive anymore! For gps i use a bluetooth gps receiver which works well if you have build in bluetooth, that would eliminate the having another wire running around problem.
The setup works pretty well for me. I found it a bit difficult and not very safe to use just the laptop monitor for navigation, while i did have it mounted fairly high up I would still have to take my eyes off the road to look at it and that's not such a good thing! That said rain would certainly destroy my setup, if i found dust to be more of a problem i'd probably mount the laptop somewhere else to shield it from the dust and then use a wireless keyboard/mouse. Although those ruggedized laptops are nice too!
The setup works pretty well for me. I found it a bit difficult and not very safe to use just the laptop monitor for navigation, while i did have it mounted fairly high up I would still have to take my eyes off the road to look at it and that's not such a good thing! That said rain would certainly destroy my setup, if i found dust to be more of a problem i'd probably mount the laptop somewhere else to shield it from the dust and then use a wireless keyboard/mouse. Although those ruggedized laptops are nice too!