The first thing you need to know about X-Men: Days of Future Past is that it's not actually the story you might know as "Days of Future Past." In order to fit in with the framework established in First Class and the popularity of certain mutants, the time setting, key characters, and metaphors (and by metaphors, I mean what metaphors anymore?) have been altered significantly. Get past that disappointment, and it turns out that Days of Future Past is the strongest X-Men entry yet.
From the opening action sequence, you know you're in for something special. Since the whole story changed, screenwriter Simon Kinberg gets to choose the perfect team of mutants to establish the stakes of the story. Nothing in the series so far compares to the excitement of seeing Blink, Warpath, Sunspot, Kitty Pryde, Iceman, Bishop, and Colossus take on the ever-adapting Sentinels in a deadly game of tag. It is the most impressive X-Men team to appear in the films so far, which is pretty impressive for only having two returning team members.
The stakes are set perfectly for Magneto and Professor X to use Kitty Pryde to send Wolverine back to the 1970s to retcon history. His job is to stop Mystique from assassinating Dr. Bolivar Trask, the scientist who creates the mutant-tracking Sentinels that destroy the world. Wolverine has to get young Erik Lehnsherr and Charles Xavier to work together after their falling out in First Class. Mystique doesn't trust either one enough by themselves to stop her plan, but the pair of them working together might save the world.
The opening action sequence is almost surpassed by the section of the story focusing on a teenage Quicksilver. Quicksilver's power is moving very fast. Director Bryan Singer and cinematographer Newton Thomas Sigel find the perfect way to bring that power to the screen. It is handled with such humor and grace that you'll fall in love with a character who appeared to be totally wrong based on the promotional images. Of course a teenage hoodlum in the 1970s would dress like an affected glam rocker and always have headphones on. He's rebelling. Against what? Whatever you got.
The jumps back and forth to the present of the story are handled well and create a good bit of tension. Unfortunately, one particular device is used before it really fits the narrative, making the better scene far less effective than it should be. There's also the too convenient arrival of more players right before things get really dangerous that detracts from the strong suspense built to that point.
Still, it's hard to imagine a superhero fan could find much fault with this particular film. It's funny, it's dramatic, it has great character development, the action sequences are clever, and the story never really drags. The conclusion is one of the strongest in the genre and is worth watching the entirety of Days of Future Past just to see that pay off.