Whether it is "worth" it is a subjective decision for the passenger. No way I can tell you what is and is not worth it for you. I can only answer for me.

I do care about where I sit and would pay $30 without question. Others may not care that much and would prefer to save the $30. That is why DL, and other carriers, offer different fare bases and associated features. Just make sure you carefully read and know what you are buying.