I've used Retin-A for over fifteen years. I buy it when I go to Mexico because it's so much cheaper.
Even after using it all this time, I don't use it every night. I use it every other night or two out of three nights. My face still peels from using it more often.
I defintely think it helps keep my skin smooth and minimizes fine wrinkles, but doesn't stop them from forming altogether. It lightens brown spots, but has to be used regularly for months to see this happen. If use isn't continued, the brown spots get darker again.
It's not a miracle, but I definitely think it's worth using.