A sexually liberated, sweet-and-sour romance buoyed by a cracking freshman screenplay and some sophisticated characterization that elevates it above the usual rom-com fare, No Strings Attached benefits tremendously from star Natalie Portman's strong centerpiece performance and a unique combination of talent behind the camera. And while few who buy a ticket will ever doubt how the story will end, the journey is the destination as Elizabeth Meriwether's vivaciously libertine story treats convention like a one-night stand while detailing the inherent flaws of friends-with-benefits relationships. Adam (Ashton Kutcher) was a typical hormonal 14-year-old when he first came on to Emma (Portman) at summer camp -- and got shot down in flames. In the years that followed, however, Adam and Emma continued to cross paths until, eventually, they both caved to their animal instincts. Despite an intense session of earth-shaking sex, however, Emma makes it clear to Adam that the last thing she wants is a committed relationship. And thanks to the fact that Adam's father (Kevin Kline), a fallen television star, has just begun dating his son's ex-girlfriend, the horrified bachelor has developed an aversion to monogamy as well. At first their casual stance on sex works great for both of them; Emma can focus on her career instead of allowing her emotions to dictate her decisions, and Adam can play the field without fear of hurting her feelings. Over time, though, a funny thing happens -- Adam begins to develop feelings for Emma that he never had for any of his countless conquests. Before they both know it, love has reared its ugly head and they've gotten too emotionally involved to cut the relationship off cold. But is commitment in the cards for the couple that always swore it would never get serious, or has the time come for them to finally part ways once and for all? Perhaps, given the dialogue-driven nature of No Strings Attached, the film's youthful take on contemporary romance, and the distinct lack of big-budget set pieces that frequently crop up in Ivan Reitman's movies, it may come as a slight surprise that the veteran director's first feature in five years plays a bit more like one of his son Jason's introspective dramedies than one from the man who brought us such special-effects-heavy spectacles as Ghostbusters, Evolution, and My Super Ex-Girlfriend -- but the result is arguably his most consistently satisfying film since the early '90s. Reitman obviously knows a good screenplay when he sees one, and Meriwether's observant, salaciously charming first effort certainly qualifies. She wastes no time in setting the frank sexual tone in an efficient, compulsively funny setup, and continues to impress with her natural instinct for comic timing as Adam and Emma's lusty arrangement gradually gives way to something of real substance. Somewhere between Reitman's assured direction, Meriwether's puckish writing style, and a great ensemble cast including Kevin Kline, Greta Gerwig, and Lake Bell, No Strings Attached strikes an ideal balance between convention and kink, continually blindsiding us with a series of witty verbal sucker punches and off-kilter character beats. All of this leads us to the film's single strongest asset: Natalie Portman. No Strings Attached hits theaters almost immediately following Portman's Golden Globe win for Best Actress in Black Swan, offering further proof that she has rightfully earned her status as one of the most talented, versatile actresses in Hollywood. While credit must be given to Meriwether for conceiving a character much more complex than your stereotypical rom-com paramour, it's Portman who instills Emma with a sense of depth and damage that doesn't weigh down the proceedings even after she's hit rock bottom. And despite the fact that we really only get a superficial glimpse into the factors that have rendered Emma unable to get involved in a committed relationship, Portman retains our sympathy by allowing the character's emotions to register honestly and genuinely as she begins to realize what she's letting slip through her fingers. Kutcher's effective blend of handsome looks and goofy charm makes Adam the type of good-hearted everyman any girl could fall for, even if the two romantic leads seem like the most unlikely of couples offscreen. The end result is an atypical "chick flick" that's sure to make the ladies swoon, and give their reluctant male companions some genuine laughs at the same time.