I cannot comment on the psychological and physical effects of having large breasts, but I know of two of my good friends, who have done it, and are very pleased with the results.
One of them had it done about 6 or 7 years ago. It really changed her for the better. She was very shy and uncomfortable in her own body before surgery and she became another person after.
The other one, had it done last year, after so much complaining that her bust size was getting "in the way" of her career, since she felt that it was such a distraction and people had to look there first. She is doing beautifully as well. I really think that whole thing was her perception, however.
I think it all depends on how much it affects you or if you are unsatisfied with your appearance.