Well, tried out the National Geographic TOPO! software with the GPS last night. First I got greedy and uploaded a huge map with all of northern NJ and a bit of PA. However, when viewed on the GPS, I found the included 100k topos to not be too helpful.

Then I tried a "Superquad" 24k map. They allow you to download 25 of these for free, additional ones cost $25 for 25 maps. These are much better.

When zoomed out, the GPS displays the base map. As you zoom in to a certain level, it displays the 100k map. The next few zooms are increasingly fuzzy versions of the 100k bitmap with no additional detail. Next it switches to the 24k map and you can actually see something. The next few zooms are magnified versions of the 24k map. Finally the last few zooms are only the base map.

Can't wait to get out in the woods with this new toy.