GPS Units ....Are these ok for general use ?

I'd suggest you chase down reviews of the products in which you are interested. Personally, I have a couple Garmin products; a handheld E-Trex Legend and a Street Pilot which is mounted in my truck. Both are updateable both as regards firmware and software. The Legend has a relatively low data capcity, and does not accommodate removeable memory media, but for the applications to which I put the unit, those are not significant flaws; I simply load the appropriate mapset into the unit from a computer, and I'm good to go. Alternatively, the unit can be interfaced with a laptop or PDA into which as much map data as may be desired has been loaded. The Street Pilot has a larger, multichrome display, offers voice prompts for various functions including turn-by-turn navigation, waypoint arrival notification, and off-route warnings. The Street Pilot employs proprietary removeable flash media available from the manufacturer in a variety of storage capacities, as well as being also capable of being interfaced with a computer, as is the Legend, for updating, to utilize a larger mapset than the unit itself can accommodate, or for a larger real-time navigation or trip-planning display. Both units will interface with and control a 'puter or PDA loaded with GPS-enabled software from just about any publisher. I don't propose that either unit I own and mention might necessarilly be best for you, I note merely I find both, in their respective applications, adequate to my needs. Your mileage may vary.