This is a pretty good thread if you're interested:
http://forum.calgarypuck.com/showthr...highlight=gps*
As I have only seen them in the wild (don't own one myself) I can only comment on the install. The ones I've seen come with a little swivel attachment that suctions to your windshield and clips into the device. You usually just have to turn it on and give it some time to find you. You can also hook them up to a computer and load additional maps if necessary.
also, big deal at dell today (but today only) $300 Garmin on for $170:
http://accessories.dell.com/sna/prod...1&sku=A2509009