I will accept a Director's Cut if the director feels they have been screwed over by the studio interferance. Sometimes, the studio takes it out of the director's hands. I'll accept them as long as the other version is available to buy. However, I don't think I've ever seen a recent movie that has been improved. Apocalypse Now is a great exampple. Apocalypse Now is a masterpiece. Apocalypse Now Redux may now be the official version, but I think it is trashy and tries to explain an inexplicable war. I'll accept it because both versions are available on DVD.
I don't consider the Lord of the Rings Extended Editions to be Director's Cuts. I think they are a seperate class mainly because four+ hours in a movie theater is torturous(especially if there is no intermission) and not cost effective. Again, both versions are available on DVD.
In Lucas' case, the only studio interferance was that result of being overbudget and running past deadline. I guess he has the legal right to change them, but does he have the moral right? His changes are not changes because of studio interferance and most aren't because they didn't have the technology. My main problem with what Lucas is doing is not just that changes have been made to the masterpieces, but that the originals are no longer being produced and have not been put on the best technology available(DVD-for now). You can get them for places on the interenet, but they won't be there for too much longer.