You can have really good results using the GPS and built in database. The key is how you set it up, which doesn't require a tremendous amount of programming skill. As others have said, set the range to 5 miles. That will limit how far out the scanner will try to listen. Second, carefully select what Service Types you want to listen to. That will reduce the amount of extraneous radio traffic you will here. Third, and this might be different for different people, turn of the "Nationwide" lists.
I spend a lot of time programming for my local area and surrounding states. Once I'm out of the New England, I use the GPS and built in database for my listening. There are just too many radio systems out there to program all of them manually.
On a slightly different topic, are you sure that you want a portable scanner for use in a vehicle? While portability is nice, it can be a PITA to manipulate the controls and see the display while operating a vehicle. The SDS200 is a great scanner for mobile use.
Either way, for mobile scanning, you will need a vehicle mounted antenna and most likely will want an external speaker. Unless your wife doesn't want to listen, in which case I'd recommend a quality ear phone.