I've been a part of a couple of them.
I think it all depends on the expectations. If you expect it to make them do anything, or change, that will probably be a problem. If YOU need it, feel it would be helpful to YOU to be able to tell them how you feel. And then, let go. Then I think it is worth it.
It can also be a good learning experience. You'll find out what you can expect from the other people who love the addict. If they can't be honest there. Or tell the addict how they feel, or what they can expect. If they can't say, "no" there. Well, when the team is gone.. and they are alone, and the addict show's up at their door, calls them. They probably will not be able to say, "no" then either.
My experience? Alot of people will talk about the addict.. but not always to them.