I don't know that I'm well-qualified to critique Cloud Atlas on its own merits. The film is, after all, based on one of my favorite books--the novel of the same name by David Mitchell. Because I've read the novel, I can't comment on how much sense the film makes; I can already fill in any possible gaps. Like most, I'd considered the novel unfilmable--its nesting-doll storytelling technique, its vast and various characters spread far across time, even its length all seemed impossible to tackle on the screen.
So credit the Wachowski siblings and Tom Tykwer, who each directed various segments of the film, with stunning ambition. Moviegoers' reactions to Wachowski projects (including The Matrix films, V for Vendetta, and Speed Racer) have not always been the kindest, but anyone can see they've got a flare for the visual and for non-traditional storytelling.
Cloud Atlas follows six protagonists from different times through their various stories. Adam Ewing's sea-faring adventures in the 1840s, composer Robert Frobisher's musical collaboration in the 1930s, Luisa Rey's political intrigue of the 1970s, present day's Timothy Cavindish's misadventures with publishing and nursing homes, fabricant Sonmi-451's battles against a technologically superior but oppressive future, and Zachry's tribe loyalties 106 years "after the fall" do not seem to have much in common at first blush. The film drops the novel's nesting-doll approach, instead jumping from one story to the next at the drop of a hat and pulling the themes and similarities between the stories to the surface, often using one character's voice-over to demonstrate what happens to another.
This may lead to some serious confusion for viewers, especially early on, but for an audience willing to go along with things for a while, the film ties its varying storylines together pretty effectively.
The film has already met with some controversy over its casting. Each of the six segments use the same actors in new roles, meaning actors play across age, gender, and racial lines. The result winds up feeling like a game of "Where's Waldo?" and winds up distracting at best, and offensive at worst. Yellowface and Blackface have a pretty nasty history attached to them, and while the cross-casting fits nicely with the film's study of identity and is clearly not done to be purposely demeaning or offensive, it might still be enough to turn some audiences away.
Cloud Atlas is, at times, kind of a mess. It will probably prove polarizing; I imagine most will come away either loving or hating it. Still, I'd rather seen an ambitious mess--or even an ambitious failure--than another mediocre, by-the-numbers sequel or remake. Cloud Atlas isn't like any other movie out there these days--and I can't possibly find that to be a criticism.