Usualy I'm against grain removal. But in certain case, when not overused, it could be okay. Like for the Aliens bluray. Cameron said that he used cheap film stock to make the budget smaller (or because it was all he had) (IIRC) so when the time for the bluray has come he tried to diminish the grain with great care. He still let some of it because it was how the movie looked but it was not the way he would have shot the movie back then. So, all in all, it all depends on who does the job and with what intention in mind and with what result... You could also say that if you don't want to do wrong: don't use grain removal. ;)