Dedicated check-in lines.

Ability to stand-by for a later same-day flight without charge -- although if AA still has an informal "flat tire" rule, I'm not sure how much of a benefit this is.

Gold -- or higher -- AAdvantage status would enable you to ditch the credit card in favor of one that might be more lucrative for travel/dining charges, and still get a free checked bag.

For me, the free MCE seats at check-in are now the most valuable benefit of my LTG status. If you're tall, those 31"-pitch seats in "regular" Coach are very uncomfortable.

Edited to add: And if JetBlue in fact acquires Spirit -- and converts Spirit aircraft to JetBlue configurations -- then your AAdvantage Gold status will give you some nice benefits when flying on JetBlue flights formerly operated by Spirit.