I've been using MS Streets 2007 for about a half year now and have to say that I'm pretty impressed with it. There are times (maybe .05%) that it won't be able to find the exact address or that the streets have changed but it's a very rare occurence. It also has Windows Live which means that if you have an internet connection, with a click of the mouse, you can see an overhead view of your area via satellite.
One of the things that I like about Streets is that it is so customizable. You are able to set up your own points-of-interest. There are databases out there for all the truck stops, weigh stations, wal-marts etc. I also put in my company's terminals. So when you plan on driving 'x' amount of miles for that day, you will know what's near by when you're ready for a break.
I don't think that there is any gps program out there that is meant to truly stand alone as a truckers only navigational device. You will always need to reference the truckers bible (aka mc atlas) to verify restricted roads, etc. But that's another thing you can program into streets. If there is an area you travel thru that does have a restricted route, you can tell streets to avoid that area.
As far as securing the laptop goes, mine is a pretty sophisticated system:
* Place laptop on drivers seat facing you
* Secure in place with seatbelt