I think Rescue was the best class I took in the "mainstream" curriculum.
It will not improve or polish your own personal diving skills, although in my class we at least practiced some emergency procedures, which I think people often haven't done since they got certified. But it will make you more aware of conditions or situations that may lead to an accident or incident, and it will give you some strategies for coping with such things when they occur. I HAVE dealt with a truly panicked diver, who was NOT part of my team, at a local dive site, and I was glad of the training.
If you want a class to work on your own personal skills, I would recommend, as others have, classes which are specifically aimed at that. Any Intro to Tech type class will work on this; GUE Fundamentals was really the first such class to be widely offered to recreational divers, and I think still is the best. If you have access to an area with overhead environments, a cavern class will focus on skills as well. Or if you have access to an instructor who has technical (or even better, cave) training, ask him to go out and do a series of "diving lessons" with you, like a PPB class on steroids.