I use a Garmin Ique 3600. It's actually a palm based pda but has built in gps. It's "old" technology but is now relatively inexpensive. With a 2 GB SD card I have several hundred ebooks on it and it also works well as an mp3 player.
The included maps are vector or "line" maps and, even with delorme upgrades, have very few gravel roads. I use a program called Pathaway that allows you georeference any scanned or downloaded map for use as a moving map display. USGS topo maps can be imported and georeferenced automatically. I keep a database with of good campsites in the unit.
Battery life isn't great but higher capacity batts are available as well as AA battery packs and 12 v vehicle adapters. There are probably better units out there but I like being able to use my own scanned maps for off pavement.
I usually carry atlas type topo maps in my travels. Note that delorme "gazetteer" atlas are notoriously inaccurate!! I've found many places where a well established road was shown in the wrong place so beware. The newer Benchmark atlas' is GREAT. While they only have a few western states at present, the different scales and good shaded relief make them very easy to use. Also, they don't end abruptly at state borders like the crappy gazetteer maps.
Just my opinion (s),
Rob