I agree you can eat any chicken. How it tastes, well, that is up to the individual and how it is cooked. I like the flavor of an older chicken but many people don't, especially if they have grown up thinking the chicken from the store is the way it should taste. I don't mind a bit if texture but I don't like it rubbery.
The older a chicken gets, the stronger the taste. The older it gets, the tougher it can be, but toughness depends a lot on how it is cooked. If you cook an older chicken long, slow, and moist, it can be very tender. If you cook it hot and dry, it can be very tough. For your first try, you might want to look up a recipe for Coq au Vin. That's French for cock and wine. It is a traditional recipe for cooking an older rooster. I think it is a great first recipe for an older bird. It usually turns out pretty good so you learn how good it can be. After you have one under your belt, you can branch out with your cooking, trying different things, but you know there are ways it can be done and it come out really good. I'd hate for your first effort to turn out bad and you think it can't be any good. You miss out on a lot that way.