Jim "from" Iowa here.
I just sold my portable GPS (Magellan RoadMate 700) in favor of PC based solutions.
PC based solutions are not for everyone however and it's hard to beat the simplicity and portability of the Portable GPS units (Magellan, Garmin, Tom Tom and others).
Because I am quite the geek/gadget freak, I am building a PC for the truck (a carputer
Back to one of your questions, I use the GPS for route navigation when we RV travel. I also travel locally for work and have programmed in all of my offices. Secondarily, I use the GPS for the POIs (point of interest). Handy when you are looking for a particular restaurant, an ATM or the next fuel stop etc.
To speak to your second question about a laptop based system, my carputer will be a small shoebox sized unit that will reside under the driver's seat. Initially, I will use a Garmin system and Microsoft Streets and Trips. I've read a lot about several other programs and may try others as well. As for connecting, I will be using 2 different magnetic roof-mount GPS antennas (due to the Garmin outputing a proprietary data protocol). As for updating the programs, that will be a function of the maker of each. Magellan (Thales) sends out CDs (upgrades you pay for). I am not sure what Garmin, Delorme and others do.
As a side note, I will have Wi-Fi, Bluetooth and GSM/GPRS wireless protocols on the carputer so I have a lot of options for getting data to the machine.
Best of luck to you and I look forward to learning what you end up doing.
Jim (formerly of Ft. Dodge, IA)