>My impression from reading between the lines on this thread is that people are using them to propel themselves along trails (hence two poles with straps good) rather than as balance and feelers off trail.
I heard about Nordic Walking last year (on BPL) and when the snow melted I began using that technique with my trekking poles. I find, when hiking on flat and uphill trails, that placing the poles just beside my feet and pushing increases my hiking speed between 1/4 to 1/3 mile per hour with no increase in exertion. I not only push back but also down, so I still get some of the weight transfer benefit as well as propulsion. (I compared speeds by hiking the same 20-mile trail several times in the same week using no poles, trekking poles the usual way, and trekking poles the Nordic Walking way adapted for hiking on trails, with and without straps.) True Nordic Walking is meant to be good cardio exercise, but I use just enough of the technique to improve my speed without noticeably increasing my cardio. If the trail is downhill or a bit sketchy I just use my poles the 'normal' way to take some weight off and improve balance.
For off-trail I prefer a single pole (often a 6-foot bamboo staff; 12 oz) and probably use it the same way you use yours. Bamboo staves were easy to get in Hawaii, and I didn't find a pair of trekking poles as useful or as easy to handle as a single pole on those rough 'trails.' (Some hikers carry a 'dirt axe' for nasty sections, so you can guess how primitive some trails are.) A bamboo staff once saved my life, at the cost of its own; they're not terribly strong when bent.
>In both cases, light and stiff are the key, no?
Agreed. The difference between 20oz/pair poles and 8oz/pair poles was much more significant than I thought. After all, my trekking poles didn't feel that heavy. But it was amazingly easy to swing one lightweight pole above head height in front of me at every other step to clear spiderwebs, and I felt that my hands and wrists were less tired at the end of the day, even without straps. My heavy poles have anti-shock springs in them, but my lightweight poles have enough bend in them to not cause any shock-related injury, while still being able to hold my body weight between them.
I'm going to try the ultralight poles that David mentioned. My nordic ski poles weigh 16oz/pair; I didn't realize that Nordic Walking poles were _that_ light! I'm curious whether they will hold up to the strain of off-trail, or even on-trail, hiking.