I've used the eMap as well and it's a nice unit. Good, compact size ideally suited to hiking and other mobile activities. I've used it from a window seat in a transcontinental flight (neat to see the ground map moving at 600mph), plotting hiking and mountain biking trails with an external antennae, and for short driving trips.

If you want something that is geared more towards automotive use, check out the Streetpilot III from Garmin. Here's a full review:
http://www.gpsinformation.net/spiii/sp3review.htm

I used my old II+ for a number of cross country trips. It doesn't have maps, but just being able to see your travel direction, accurate speed, as well as cumulative or remaining miles is fun. You can pre-load waypoints (hotels, cities, etc...) and it will tell you which direction and how far they are from you. I drove from NH to CA one year and setup the GPS to make a track log (like dropping digital bread crumbs) with a sample every five minutes. After the trip when I overlayed this log onto a US map you could see not only where I drove, but also areas of construction or higher speed limits. Since it recorded the position at a fixed time interval the dots would be much further apart in Nebraska with a 75mph speed limit than in New York with a (at the time) 55mph limit. Construction or side roads would show up as a traffic jam of "dots."

BTW, you'll find other reviews and GPS related info at:
http://joe.mehaffey.com/

One of my favorite things about the newer GPS's is that you can download updated firmware off the internet. It's worthwhile to check Joe's site or the manufacturer's just for that reason. Also, depending on where you live (and what interests you), you can download free topo quads for plotting trails pre or post-hike/bike.

Here are my favorite GPS computer apps:

PC - http://www.oziexplorer.com
Mac - http://www.gpsy.com

You can also get or plot lat/lon coordinates at www.mapblast.com