"It's Complicated" is a sophisticated and intelligent comedy. The direction and acting demostrate the virtue of experience and maturity in the making of a movie.
Meryl Streep is one of the few actors living now who can do both comedy and drama well, while Alec Baldwin and Steve Martin are wonderful comedians. Finally, this is the first movie with John Krasinski in which I've seen signs that he may outgrow the mugging, eye-rolling Jim of The Office. In "It's Complicated," Krasinski was a BIT more real.
Often in comedies, I find that I've seen all the good parts in the trailers. This was not true for "It's Complicated" ....it kept me laughing and engaged throughout.