I love it because the funny threads make my blue days a bit lighter. I am often howling at the screen, tears running down my face, wishing I had an nth of the wit that some of the posters have.
I am also grateful that I can pick up tips in various guises.
BUT most importantly, the serious threads force me to challenge my own viewpoint. Quite often my POV has been turned if not completely, then slightly. So it also keeps the ol' grey cells from diminishing quite so fast :)