I have been flying alot for the last five years and was wondering if it is worth staying with Delta or moving to another airline. I generally fly 150,000 to 250,000 qualifing miles with Delta and about 30,000-90,000 qualifing miles on Northwest (flights that doesn't share miles with delta). I live in Cinicinnati and that is the reason I started with Delta and never really flew anyone else. What is your opinion of American vs. Delta or United vs. Delta?