What do you lose by watching the 1977 version? Dolby Digital 5.1 EX sound, for one thing (only 2.0 Surround here). Digital cleanup for another--Tatooine looks like it's been coated with an additional layer of sand cloud. But for home-theater owners, the biggest frustration will be from the non-anamorphic picture. On a widescreen TV, an anamorphically enhanced (16x9) picture at a 2.35:1 aspect ratio will fill the screen with the exception of small black bars on the top and bottom. The original edition of Star Wars, however, is not anamorphically enhanced (sometimes referred to as "4:3 letterbox"), so on a widescreen TV it will have large black bars on the top, the bottom, and the sides unless you stretch the picture (and distort it in the process, especially considering the substandard picture quality). If you're watching on a standard square-shaped (4:3) TV, though, you won't notice a difference.
Yes, it's true that serious home-theater lovers who want spectacular sound and anamorphically enhanced picture can always watch the 2004 version of the movie also included in this set. But chances are good that they already picked up the trilogy edition of all three films, so their decision to buy the 2006 two-disc edition depends on how much they want the original film. The official LucasFilm stance is that this is an individual release of the 2004 version of Star Wars: Episode IV, A New Hope, and the 1977 version of the film is merely a "bonus feature." Common speculation is that the only reason the original versions are seeing the official light of day at all is to undercut the booming black market for the laserdisc version. Star Wars fans will have to decide for themselves if that's worth the purchase. --David Horiuchi