I really enjoy the tree maintenance part of rec climbing, removing hazards provides interesting challenges that enhances rec climbing. Others have mentioned this but I wanted to revisit the topic.
Sometimes when I'm working in a tree I feel like the equivalent of a dental hygenist, cleaning out a bit of rot here, trimming a dead branch there. Kind of payback for the privilege of climbing the tree.
Another thing to consider is not to be overzealous in this kind of tree maintenance, various bird species and other animals depend on dead branches for food and shelter. It's another interesting problem trying to figure out which dead stuff to leave alone, it's part of the life of the tree too.
-moss