I used to own one at the the start of my climbing career. I gave it away and now I do not even carry one. It is up to you to have one but it depends how high your trees are, how fast you want to descend from the tree, etc. Some people use them others do not even own one. I mostly use split tails to climb DdRT so they work to get me off the tree.
I own a Grigri that I use for SRT climbs but I do not carry it with me every time I go up in the tree. Moss will chime in with more inside from his prespective and experiences.
