The movie is all science-fiction cliche, knows it, and revels in it. While the ubiquitous ads only give away the first third of the movie, suffice it to say you're not likely to be surprised by much here -- the plot is *entirely* predictable three steps ahead.
That said, though, it's a great ride. The writing is crisp, and things zing along at a quick pace. The characters are all appealing, even the over-the-top-and-out-the-roof alien villain. (Not to mention Stephen Colbert as the President.) It turns out to have a strong viewpoint character: Susan, the white-haired giant woman in the ads, played by Reese Witherspoon, who is quite clearly the protagonist. (And is playing roughly the same character as Elastigirl from the original Doom Patrol comics.) Indeed, from a comic-book point of view, this movie comes across as nothing quite so much as the birth of a superhero: watching her grow into her very large skin is much of the fun of the story.
The animation is as good as one expects these days, and the 3D is remarkable: it gets the gimmicks out of the way early on, and then settles in to just doing it really well. I traditionally have problems with 3D glasses, but it was seamless here -- the effect worked well enough that I could mostly just experience it, rather than *thinking* about it. And this is a movie that benefits from the IMAX: in every respect, this movie is *big* (indeed, "big" is a recurring theme -- Susan is far from the biggest thing in here), and the big screen suits it well.
Overall, while it's not one of those cultural-event movies that you *must* see, it's well worth the outing. Funny and smart enough for the parents, nice enough for most kids. Recommended.