IMO, Jonathan’s maps are the way to go. Be sure to get the latest addition, 2010, because there are changes every year. A GPS is a positive plus, it WILL tell you where you are and save a lot of miles (trust me). If you are thinking of more definitive maps, like for the Northern Wind River Range, they can be purchased through different organizations like Earthwalk Press and be picked up before hand or along the way at certain outfitters. Unless you want to do side trips, they are not really necessary though.
Lessons learned:
Print the maps on larger paper (numbers, letters and contour lines are hard to read at times). There are different “type” maps used throughout the trail.
Check the print quality periodically while going through the process (it takes a lot of ink to do).
Faded maps are hard to read, especially the color blue (blue equals water).
Recommend one side only, this way you can put them together for a bigger "on the ground " look at things.
Newer objects like power lines, are not indicated on 95% of the maps.
Technology is great as long as it works (GPS). Batteries fail and if the wrong info is put in? You get the idea.
Trust your compass, always orientate your maps before looking at them.
Let the map tell you where you are, not the other way around.
WB, CDT09