I treat Extended/Unrated Editions like I treat DVD/BluRay double dips. What does it add, and why?
GOOD EXAMPLES
Lord of the Rings Trilogy: While the theatrical versions are nice, I will always prefer having more time to spend in Middle Earth with scenes that add a good amount of depth to the universe and it's characters.
Blade Runner/Brazil: Classic examples of directors having two different viewpoints on how they prefer their films should be presented, but include the original studio edition to show just how much conflict there was in making the final cut.
Alien Anthology: Always found it funny that of the four films on this set, the alternate cut of ALIENS was the only true 'Director's Cut' out of the whole bunch, even with ALIEN's alternate cut labeled Director's Cut, which Scott himself said was purely for marketing. What makes the anthology unique is that every film's alternate version are not like the other one. Alien was re-edited to fit with modern day editing in mind, ALIENS was a true alternate version that the director preferred, ALIEN3 was a rough cut version that reflected David Fincher's attempt to get it to theaters before reshoots took over, and ALIEN Resurrection was a case of bringing original conceptualized material to the film with it's alternate opening and ending.
BAD EXAMPLES
Unrated Comedies: I remember seeing the first Unrated DVD of American Pie and wondered "Wow, they really cut stuff out of this R-Rated comedy?". But when I watched it, the differences were so minor and so irrelevant that I used it as an example on how the MPAA is really incompetent. Probably the worst Unrated version of any comedy would have to go to The Five Year Engagement. For a not-so funny comedy that clocks in over two hours, the extended version was pure torture.
Bootleg Quality: The Director's Cut of Army Of Darkness is a pretty interesting take on the cult classic, it's just a pity that the quality of the material used for it was down right unwatchable. Some scenes will look good, while other scenes will look like it was from a third generation recorded VHS tape.
George Lucas: Of all the changes that Lucas has made to his Star Wars films, I think only 15% of the changes actually benefited the films in a positive way. Things like FX clean up and enhancing battle sequences with new effects. Where it gets downright awful is the inclusion of forced comedy that was never there (New Tatooine intro), VERY POORLY DONE FX (CGI ronto just walking in front of the camera), new scenes that add nothing to the story and actually diminishes certain characters (Jabba's inclusion), and replacing original actors with prequel actors (Boba Fett's voice, Hayden's head). But the worst crime that I think everyone here knows is how Lucas seems adamant about never releasing the original, unaltered versions of the film. That's unfortunate.
Family Friendly Editions: Really?
MIXED EXAMPLES
Enhanced Audio: This one is really tricky. Films made on a tight budget with tight time constraints can be quite noticeable in the audio department. The original TERMINATOR for example used a ton of stock audio to the point where every explosion and every gun fire sounded exactly the same. The new remix certainly adds a lot more diversity in the sound department enough that I prefer listening to it than the original, it does give the film a bit of a modern feel that most would consider out of place. Same goes for Scarface that, unlike the new TERMINATOR mix, has a new sound mix that really came out amateurish.
Unannounced Changes: This one is really a mixed bag. This is when alterations were done to the film but were never announced. Battlefield Earth was released on DVD with an alternate cut of the film that got rid of a lot of bad scenes (Can humans fly?) but it was never stated. The BluRay to Blue Thunder features a soundtrack where some elements of the score have been re-edited entirely. Scenes that didn't have music now have it, music starts a bit later in some, and one scene with Lymangood being chased by a car features completely different take on the score.