I have no personal experience with this but when I was considering trying this for the FLUTD cat I have here, I came across this link. People who have been using it successfully for years are suddenly having their cats get sick with intestinal problems. There is no recall YET but be careful especially if buying new bags. The problem seems to be mainly with the dry food. Read the reports and make your own decisions.
http://www.consumeraffairs.com/pets/royal_canin.html
http://www.consumeraffairs.com/pets/royal_canin.html