First, by portable, do you mean in-vehicle or handheld? Almost all GPS units, with the exception of in-dash units, are "portable". If you are looking for a unit for both vehicle and walking/hiking/hunting applications I would highly recommend the Garmin GPS60CSX. It has many useful features for hiking but will also do a good job in-vehicle with the right mapset. The problem is the memory does not allow you to load the entire country at one time - you can load about seven states at a time using Map Source. If I were buying a new GPS today (I use the Garmin 680 inv-vehicle)for the truck, I would look at the Garmin GPS 7XX series. Go to
www.gpsreview.net for some good reviews on GPS. The reason I like the new 7XX series is the capability to do true route planning, the advanced turn feature and the overall usability of Garmins. It has a good WUF factor. (Wife Usability Factor). Nuff said.