I have watched R-rated movies for as long as I can remember. I don't really understand what the big deal is. I understand that there are concerns with people seeing too much nudity and violence but, for the most part, young children are not interested in those things. If you keep kids active and don't rely on a television as a babysitter what your children are watching will never become an issue.
Uftah, gotta fill up 50 words here. We watched several rated R movies, even before the age of 10. Lethal Weapon, Die Hard, Commando... These were just movies we had in our house that us kids would watch when Mom and Dad were away. We didn't have cable, so couldn't watch too much TV-MA stuff.