Again, that's what I've heard. Perhaps they weren't entirely invisible, but were certainly far less noticeable than on the home video releases. Whether you saw the Star Wars movies on the first days of showing, and thus the print was in great shape, and whether the projector was setup properly may also be factors, not sure. But on opening day, with a good projector and skilled projectionist, they were either not visible or much less so than you see on home video, but I'm not an expert on the subject. Post a question for "zombie" in the Star Wars thread at the link below, he can give all the technical details.

In any case, they were certainly never intended to be seen, so naturally we want to make the restored version look the way it was intended to look at theaters on opening day, that means no matte lines.

http://boards.theforce.net/classic_trilogy/b10002/24990319/p42