I've not found much use for CLEAR vs precheck. BUT, I need to be in OAK a bunch now, so am thinking maybe it could help at the Southwest mess (much worse since the new scanning machines). My wife just enrolled at LAX UA T7 and said it was super short line, but didn't think it helped her much. I enrolled but haven't tried it yet.

At OAK, it seems to let me skip to the front of the precheck line which might be helpful, but, outside of very specific airport setups I don't know why anyone would pay the fee out of pocket (vs cc benefit).