I didn't really think about this as a permanent replacement to smoking, but now that I do: I would totally rather use my lungs to smoke than my mouth.
Lungs are actually made to filter things out of the air and clean themselves to keep going. I'm not saying they were made to smoke pot all the time, but they were much more desined to deal with smoke than your mouth.
I think if I smoked in my mouth like that everytime I smoked I would develope all kinds of mouth problems. Ever seen what chewing tobacco does to mouths, how about meth. Not saying it's the same, but nasty shit happens to your mouth, gums, teeth, and throat with constant abuse. And unlike your lungs, who with time should clean and heal themselves, your mouth does not have those regenerative properties.
I'm no medical expert so this is all my opinion, but yeah I'd rather caugh than have no teeth. And if I didn't want to caugh I'd buy a vaporizor.
HOWEVER, I still think this is perfect for my wife. She can't handle actually smoking, and on the rare occasion she needs/ wants to smoke (6 times a year) I just blow smoke at her (watered down shotgun). It (i think) would be nice for her to try this as an alternative.