Before we get into this, I would like to clarify that this may have slight spoiler in it, so tread carefully.
X-Men: Days of Future Past for me was the best X-Men film so far, and for good reason, it has action, heart, laughter, and darkness, the perfect combination for a great movie. And the extended edition proves to improve upon a great film.
An obvious positive, but I will state it anyway, the extended version has allowed the insertion of an important character. Hence the name 'Rogue Cut'. I was worried that Bryan Singer would illogically force this character into the extended edition. But the story opened up in other areas for Rogue to fit it. Which allowed Logic to take its natural course.
Another big positive is that it allows for characters in both future and past. This allows for necessary character development for important characters, such as younger Charles Xavier and Magneto. Which makes the story all the more satisfying when the big moments are happening.
My only negative about this extended edition is that it allows for Mystique and Beasts relationship to fester into something more serious. Just like in X-Men: First Class, leaves me to wonder why they together because they are VERY different people. I sense this will spill into X-Men: Apocalypse, which will be a poor story-line in an already dense story-line. A small negative, I know, but one I felt to address.
Overall. The extended edition increases the depth of character and story, which helps enhance the film overall. It is definitely worth a watch, especially in Blu-Ray.
So what do you think? Comment below an let me know!