I have large boobs, they have always been on the saggier side. I guess thats what you get when you have 40F boobies. Argh! I still go with out a bra sometimes but I am more comfortable having the girls supported.
takes a lotta uncomfortable pressure off them, and it's nice to be able to walk without someone staring in awe at your chest.
I don't wear a bra, and my boobs aren't sagging; they're relatively small (last time I wore a bra I think it was 36B), but haven't sagged at all since I stopped wearing one.