In addition to the benefits others have mentioned, they also keep your arms moving, which prevents edema/swelling in your hands. I find that if i hike more than about an hour or so without poles, my hands swell uncomfortably. The poles have always prevented that (you can also use thumb loops on your pack to get your hands up, but that doesn't work nearly as well for me, not to mention makes me feel a little unbalanced)
Add me to the camp of 'never hikes without em'
=) tif
