I have two manual pole-saws, one Stihl (21'?) and one shorter telescoping fiberglass handle (15') that I mounted a Silky blade on. I prefer the Silky, as it cuts better than the Stihl. I use the pole-saw quite a bit in my work, but can't remember using one for freeing a hung up tree. If removing a small branch or two would free the hang-up, then yes I can see that. But if you're thinking about cutting through the top of your tree, that's problematic on two counts. First, you're likely to get the saw pinched in the cut (unless you try cutting up from beneath, and good luck with that), and second, even if the cut doesn't close on your blade, you're likely cutting at a steep angle that will wear you out long before you complete the cut.
For dealing with hung up tops, there's three common methods better than resorting to a pole-saw. First, I usually cut away at the base of the tree--very carefully and studying each cut, as this can be dangerous if done wrong. Most times this works fine, but experience and caution should guide you on this. Second, a cant hook can often be used to roll the hanger to one side. (Did this with a hanger two weeks ago--and rolled the tree to the ground in under a minute.) And third, using either a come-along or a vehicle, pull the hanger out with a chain or rope attached to the base of the tree. This is the most time-consuming method, but probably the safest.