That should be more than enough camera.
I must plug the Canon g10 again... Unless you've got your heart set on super wide or really long lenses, this sweet point n shoot is 14.7 megapixels and much newer than the Nikon you're looking at, not to mention much easier to lug around on long hikes. If your looking to casually take pictures, yet have the ability to capture some great detail and use all manual settings, get the Canon. If you want to seriously get into photography and plan on investing more time and money into it, than go for the Nikon SLR. Just my two cents...
Take a look at Grasshopper's photosets, they're pretty darn phenomenal. One would never guess he's using a point and shoot, but he's got the g10.
"Arizona is the land of contrast... You can go from Minnesota to California in a matter of minutes, then have Mexican food that night." -Jack Dykinga