I too was a resistant convert to trekking poles but, now I will not go backpacking with out them. They revolutionized my backpacking experience. If I am going to do any combination of carrying a load, hiking long distances or hiking over steep terrain, I can't think of a good reason not to use poles.
Can you think of any bipedal animals that live in an alpine habitat? No! O.k., birds, but they have wings... The bipedal design sucks for steep terrain; quadrupeds rule in the mountains.
One of my favorite things about poles is that they give your arms something to do instead of just dangle there like dead hunks of meat. I love the low impact, full body work out I get hiking with poles. Of course, some people use them solely for balance, but I really like putting a little weight into them.
I Own two pairs of poles:
My first pair is a set of killer Leki poles with anti-shock springs and angled cork grips. They are the Cadillac of poles and are super comfy to use, but heavy.
My second pair are REI Peak UL's (which are made by Komperdell). They are three piece carbon fiber poles with simple light weight handles. Carbon fiber is the strongest, lightest, load bearing material available. I take the UL's over the Leki's every time. Light weight poles are a joy to use. I also really like the ability to change the length of the poles for extended uphill or downhill sections of trail and for setting up shelters.
Also, I'm all about using straps. Like others have mentioned, they let you relax your grip while using the poles, which I think is a big plus.