(all refers to non-powered pole saws)
One of the silliest things is using pole saws on lower limbs, just to climb on past them to get the ones that can't be reached. Cutting dead wood with a pole is really much more difficult than attacking it with a handsaw. You have little control using the pole where in a climb you can rope it, sling it, etc to control it. With a pole, many would come in from the top and you'll create underside 'peels'. An undercut is difficult because you can't really cut on the underside of the limb when you're under it, I don't care how good you are.
If I have a partial snapoff limb hanging on cable or phone lines and the diameter is too big for pole pruner/bull loppers, the pole saw is indispensible. Cut to this side of the line, cut to that side of the line, you're off the line.
I find pole saws really hard to use, so I'll use it as a last resort, generally speaking. When it comes in handy, it comes in very handy, but it's not a tool I'll use all day long. It depends on the guy, but myself, I'd far more prefer to climb the tree and get more intimate with it. A pole saw definitely has it's place in the arborist's tool arsenal.
