My anticipation for this movie started right after seeing The Wolverine. It was clear to me then that The Wolverine was the start of an attempt to revitalize the Bryan Singer X-Men series. Seeing the return of Professor X along with the return of Magneto's power immediately gave me the impression that the producers were aimed at undoing the way the first trilogy ended. With the release of Days of Future Past, it is an incontrovertible fact the film accomplishes this goal, for, because the film's composition is a consistent cohesion of powerful motivations, uncompromising action sequences that enhance the emotional relevance of its conflicts, and clever incorporation of comic book elements, the positive impact of this film uncannily places the X-Men film franchise back on the Marvel motion picture map while effortlessly drowning out the unavoidable--yet minor--plot inconveniences.
One prominent question I saw lingering since The Wolverine is the exact nature of Professor X's return from the dead. While the end-credit scene of The Last Stand resolves this question in an unrefined manner, it was later revealed that the writers that intended for the braindead victim to be the twin brother of Charles Xavier. While this explains the retention of Professor X's physical appearance, it critically lacks any explanation for his perpetual paralysis in the revived state. Though the explanation I had conceived a while back is far more mundane and less coincidence-reliant, the outstanding work of the writers of Days of Future Past has made it of issue in accepting the former explanation.
Another question I briefly glanced at earlier in this thread is the nature of Wolverine's reacquisition of his adamantium claws. The first and most probable solution is adapted from the comics, in which his mutant healing powers altered the metal's molecular structure to operate as an extension of his healing mechanism. I think this is the more favorable explanation, overall, because the apparent healing of the metal had already occurred when Origins established that he had been shot by a bullet that penetrated the adamantium layer on his forehead, which steadily remained as his skin healed over it, yet does not appear in the X-ray Jean Grey makes in the first X-Men. If there should be a reason for this to be infeasible, then the second and probably only remaining explanation is that Magneto, working alongside the X-Men, somehow used his powers to restore the grafting. But, as aforementioned, this is less consistent, due to the fact that the film series has strongly implied that Magneto is only able to levitate it with his magnetism in the films, with the only person verbally stated to be able to "manipulate" it being Stryker. Like Xavier's return, this is also really not an issue.
But perhaps the greatest imprintation we're left to wrestle with at the moment (as it will undoubtedly fade with a whimper) is that potentially none of the historical events that occurred in the first timeline is carried over in this new timeline. Even the question of Wolverine being either natural-boned or adamantium-bonded is left open at the end. Indeed, the X-Men series has been rebooted, and rightfully so--as the return of Cyclops is accredited to this, but more importantly it is done in a manner that has allowed the series to retain the original cast, thus making it an untraditional one. This may have been what the director of First Class meant when he said that this film has no bearing on the original storyline while the most of us were arguing the contrary by reason of its identical casting.
All in all, an absolutely brilliant work in not only the revival of a franchise, but also in the bold display of creativity that the producers are able to yield for the new direction of this saga, thus bolstering the confidence and anticipation in all viewers. The only tragedy to be witnessed at the theaters is that this movie failed to make it on the Imax screen, despite having its integrity ranking right up there alongside The Winter Soldier.