Just gonna weigh in here in case anyone thinks my opinion matters:
1. Burning plant matter and inhaling the stuff that comes out is bad for your respiratory system and probably causes cancer to boot. There are no known exceptions.
2. For God's sake, just talk with some long-term pot-heads for a while (BEFORE you start). Those people are forgeted up. They breathe and talk like tobacco smokers but they think very slowly and make boatloads of cognitive errors. Their long- and short-term memories are also pretty shot.
Seriously the burden of medical evidence today is still to prove that marijuana is extremely healthy, because the long-term detrimental effects are freakin' blatant. Not that I expect any such proof will ever occur, because really, what does it do? Releive pain, lower stress? There's plenty of ways to do those things without getting high. Marijuana users who consider the above two points and do it anyway simply hate life and want a taste of oblivion now and again. Sorry, but the universe is too awesome for me to intentionally lower my capacity to experience and correctly understand it, even assuming it were briefly.