I am using CoPilot Live, the version i have runs on a PC, the GPS receiver is a small unit that connects via a USB port.
The software was created by one of the main players in the trucking industry, ALK Technologies, http://www.alk.com.
In addition to being able set for fastest or shortest routes you can also tell it you are an RV, select from a list of heights, 13' for me, and whether you carry propane (haz mat restrictions) then it takes all that into account when it plans the route.
I use my laptop for everything including email/web surfing while on the road (love that PCMCIA Broadband card). And the CoPilot software allows you to get on-the-fly traffic updates, and my favorite feature is being able to invite people to watch your progress on the road via a web page. It will even let you and the people you invite send text messages along the way.
My mother sent us one after my sons wedding that said something to the affect that I never call but at least she knows where I am. And a friend likes to point out special POI along our routes, did you know that there really is a two story outhouse and that you can get canned armadillo?
I put my laptop on the center console with a rubber pot holder as an anti skid mat. Gives me a large screen to see, its tough getting old, and safety mode which just gives you a blue screen with BIG text and arrows while traveling at high speed. As you come up on a turn it switches to map mode.
Hope all this helps, happy trails.