Trekking poles kept me alive. Seriously - without them I would have fallen down a very steep hill several times. I hiked into Big Sur/Ventana wilderness last weekend, and all 10 miles of the trail run along the sides of steep hills/ridges covered with poison oak and trees. There were at least eight trees down across the trail and I was wearing more than 25 lbs of dead weight on my back... without the poles to keep me upright I would have had to take off the pack and crawl over/under each of these. I nearly fell as it was, and the poles took most of my weight without breaking (Komperdells, on sale from backcountry.com when I got them). I also used them while fording the Big Sur River twice, and to fend off the shiny green leaves of poison oak, and one feisty Jack Russell terrier. Used properly they take some of the weight off your back/legs and they really helped on ascents and descents, particularly when I was really really tired on the last couple of miles going out.

I did not know there were trees in the trail, and the guidebook said nothing about the river crossing being so deep and swift. I intend to take the poles on any hike of any length where the trail isn't paved/busier than a freeway at 5 pm. I should add that I was a serious doubter, even after using them on 8 mile day hikes, because they do seem like just something else to carry - but I've found they really do make a difference, and at some point I don't doubt they will come in handy as tarp poles.