It’s a story as old as the movies themselves, yet Friends with Benefits manages to keep it fresh. Boy meets girl. They forge an immediate friendship, with an easy-to-spot sexual chemistry they try to ignore. Then, almost on a dare, they hop in the sack, vowing not to let it change their relationship. Romance is a complication they would prefer to avoid.

It doesn’t take a clairvoyant to see where this is headed. The boy is Dylan (Justin Timberlake), a gifted art director about to move from L.A. to New York, where a dream job at GQ and a laughably luxurious Manhattan apartment await. The girl is Jamie (Mila Kunis), a headhunter who greets him on arrival.

Seduction isn’t part of Jamie’s sales pitch, but she and Dylan share an honest, playful banter that never feels forced. Watching them drop their guard, speeding past superficial pleasantries to reveal depths of feeling that transcend romantic-comedy clichés, is one of the movie’s real pleasures.

It’s a given that their no-strings approach to intimacy is going to backfire, and that emotions strong enough to break their friendship or elevate it will eventually take over. Benefits, a perceptive, physical farce that pokes fun at Hollywood fairy tales even as it slyly embraces them, doesn’t mess with the formula, and that’s just as well.

What the movie lacks in suspense it makes up for with its refreshingly candid depictions of sex – in particular, those clumsy, awkward moments rarely seen in Hollywood imitations of life – and with assured performances by Timberlake, Kunis, Woody Harrelson and Richard Jenkins, who keep the proceedings grounded even as romance takes flight.

Director Will Gluck, whose Easy A was one of last year’s most unexpected delights, has a formula too, and it works: He respects his characters, who are smart and sufficiently self-aware to see that their best-laid plans may be falling apart. They push forward regardless, because their hearts dictate as much, and because they are foolishly confident they can outwit love.

No dice there, and for that we are grateful – Dylan and Jamie are one of those rare movie couples who truly deserve each other. They can be thoughtless, thickheaded and frustratingly oblivious to their own feelings, as mandated by the mechanics of a well-worn plot. Yet their foibles are funny and endearingly human, qualities critical to a comedy where the journey is infinitely more interesting than the destination.