Yes, one thing I love about James Cameron's extended cut movies is that the extended cut is almost a completely different movie from the theatrical release. The Abyss is the most marked example of this. ALIENS is probably the second most standout example. I still have yet to see the extended cut of Avatar to see if the changes are as radical as in the previous two examples.
Hell, Terminator 2: Judgment Day actually had three different cuts... the 2hr and 20 minute theatrical, the 2 hr and 35 minute extended cut, and the hidden extended cut which adds even a few more scenes or makes certain changes to the narrative....the hidden cut would have to be accessed via a special remote control trick.
Alien 3 is another one of those movies (David Fincher, director) where the extended cut makes it almost a completely different story. The additional 30 minutes of footage made it about as long as the theatrical cut of ALIENS before it.
Ridley Scott actually released the director's cut of ALIEN theatrically on one night, Halloween, back in '99 I believe. He actually trimmed several segments to increase the pacing of the film. This was also offset by the couple of scenes that he restored to the film....but yeah, for all that, it still resulted in being a marginally shorter film than the original '79 release.
Overall, I believe I got my money's worth out of the Quadrilogy (and later the Anthology on Blu-Ray.)