In my case the hobby has been a very positive addition to my life.
As to your first question, my time with the beautiful and talented ladies I have been with almost always gives me joy; that's the whole point. Sexual satisfaction by its nature gives one a better outlook on life, and where better to obtain such satisfaction. The civilian world does not provide many paths to sexual satisfaction, as relationships contain a vast variety of elements, sex being a small part. Indeed, both sexes spend such enormous amounts of enegy seeking sex, and almost invariably end in a relationship where the sexual aspects are limited, and in many cases ultimately frustrating for both parties. I believe I am a better, happier and more productive person because I am not beset by sexual frustration, and ultimately that benefits me, and all those around me.
As to your second question, the modern world lacks dark corners, and time spent in dark corners is necessary to fully actualize a human being. Abe Lincoln said he would never trust a man without a vice. In our time, where everything is out in the open and everything is clean and shiny, we have no opportunity to explore, once again paraphrasing Lincoln, the darker angles of our nature. By having a part of our lives which is completely private (and this is assuming you guys are able to keep your mouths shut about your exploits), we are given an opportunity for repose and reflection that our daily lives does not provide. I think it is not only enlightening, but healthy. Certainly for those of us with high stress lives, the ability to step into another life for a brief moment makes that stress much more bearable.
As to your last question, it is not so much a question of change, as it is a question of giving confidence in ourselves. The hobby provides us with confirmation that we are able to give and receive pleasure, and communicate on a more primal level. Again, these are sadly opportunities not always possible in the civilian world. It may be particularly lucky in that most of the providers I have encountered have been warm, generous, intellegent and entertaining companions, but from many of the comments I have read on the boards, I don't think I am unique in such experiences.