Synopsis: The plot centers around a supposed "cure" for mutancy, or rather a way to suppress the mutant gene and its far-reaching implications for humankind and mutantkind alike.
Points of interest: Parallels some of the X-men comic's best story arcs, the most notable being the Dark Phoenix Saga and the recently proposed (in the comics) notion of Omega-level mutants [called Level 5 mutants in the film]. The film's ambiguous ending(s) may foreshadow elements in the proposed Wolverine and Magneto films.
Review: X-men: The Last Stand is the first of the X-films to not be directed by Bryan Singer (Singer went on to direct Superman Returns, opening in June). 'Last Stand is the third installment in the highly successful franchise and picks up where the previous film X2: Mutants United left off. Directed by Brett Ratner, the film opens in the past with Professor Xavier and Magneto's first encounter with an adolescent Jean Grey [Xavier and Magneto are still friends at this point]. From there, the film jumps forward to more present day events, the most pressing of which is a supposed "cure" for mutation.
As with the previous two films, prejudice specifically, prejudice against mutants is a central theme. This time around, however, the advent of a "cure" for mutation drives the film's themes more in the direction of self-acceptance. Many mutants seem interested in the option to become "normal". Rogue, in particular, fancies the idea of being cured of her "affliction". In this way, mutants actually break into camps based not solely on opposing humanity (or co-existing with it), but on the basis of whether they can accept themselves and their "gifts", or whether they want to be "cured" of them.
One of the biggest complaints leveled by critics against 'Last Stand has been a perceived lack of character development. When one considers the sheer number of characters in each film and especially in this film this becomes a moot point. Aside from the core cast of Professor X, Storm, Magneto, Cyclops, Jean Grey, Rogue etc., there are a host of new characters introduced this time around. Some like Colossus and Pyro were introduced in previous installments, but are given more visual (if not integral) parts this time around. Others like Kitty Pryde, Callisto, Juggernaut and Arclight are comic book favorites, but not given much else to do (but perform in fight sequences).
Overall, X-men:The Last Stand is visually superior to its predecessors not a great feat considering X2 visually outstripped the first X-men movie. Also, 'Last Stand is easily the most action-packed of the X-film's thus far. The film's fight scenes are interesting in particular the extended fight sequences between Storm and Callisto. Indeed, Halle Berry receives more screen-time as Storm this time around, and the obvious infatuation between Wolverine and Jean Grey boils to a head and is given pivotal importance to the overall story. Kelsey Grammer turns in a rather clichιd (but forgettable) performance as the blue-skinned Beast (aka Hank McCoy).
Most enjoyable about the film was Jean Grey's evolution to Phoenix (or Dark Phoenix). Also, diehard fans of the X-men are at last treated to Magneto's. [You'll have to see the film for that].

Pros: More screen time for Halle Berry as Storm; arguably the most action-packed of the series; the story isn't swallowed up by Rogue's inability to to touch other people (though that is certainly a developing sub-plot). As usual, Sir Ian McKellen's portrayal of Magneto and Patrick Stewart's as Professor Xavier largely carry the film.
Cons: Nightcrawler (portrayed by Alan Cumming in the last film), who was introduced in the last film and is a fan favorite is curiously absent. Mystique (Rebecca Romijn) and Cyclops (James Marsden) are horribly underused.
Word to the wise: Don't leave the film before watching all of the credits roll by X-men: The Last Stand features an exciting twist at the end!