Headland does yeoman work in all facets of her film. There are still some rom-com tropes and cliches, but in the overall, she manages to make an old story feel new, or at least present the viewer with enough assets to keep them in the world. In a post-They Came Together world, it's especially difficult for romantic comedies to feel fresh, but Sleeping With Other People combines several strong scenes with a liberal sprinkling of jokes. The plot isn't exactly breaking new ground, as two damaged people make each other better, but individual pieces wildly succeed in deepening the viewer's understanding of the characters. For example, Headland is able to walk a tightrope on Lainie and the doctor. Scott plays him with such detachment that it alone would be enough to communicate the cruel one-sidedness of their relationship, but a scene of them having reckless sex is filmed artfully and ecstatically, thus allowing the viewer into Lainie's head and understanding why it's so hard for her to walk away from this jerk. Headland writes and directs her characters with an empathy rarely seen in these kind of films, where often the main relationship is based on the appeal of hot people living happily ever after.
Between the two leads, one emerges more worthy of rooting interest. Brie is simply a more likable person than Sudeikis, and that comes through in their characters as well. Brie does have the easier job, having been written more sympathetically, but she still nails Lainie's frustrations while retaining the bubbly vulnerability that Brie brings to all of her roles. Jake is written as a smarmy douche with some redemptive qualities, and that fits Sudeikis to a T. Based on their presentations, it's easy to want Lainie to succeed without feeling much of anything for Jake. Where Lainie's character teaches young children and is trying to rekindle a medical career, Jake just sold his tech company for millions and lazes around the office. Where she is trying to end one destructive relationship, he is having multiple trysts and hitting on his boss. Lainie's stakes are much higher, resulting in an empathy gap that a better film would have balanced.
Further down the call sheet, Headland staffs stock roles with more great actors. As the secondary love interest for Jake, Peet is the best of a strong bunch. Her character is where Sleeping With Other People really distinguishes itself, turning a character that is usually rooted against into the heart of the film and contributing to a bittersweet ending not often attempted in romantic comedies. Peet's experiencing a career renaissance and has rarely been more compelling. Scott could've taken Sudeikis' role, having played a similar one in Friends With Kids, but he is also great as the doctor, simultaneously despicable and worthy of dignity when the traditional rom-com revenge segment goes wrong. The classic supportive friends are here, including Jason Mantzoukas (reprising his role of Supportive Friend in They Came Together), Natasha Lyonne, and Andrea Savage, and while Headland isn't exactly turning the genre on its head here, she gets points for casting cool people. On the downside, as a counterpart to Peet's Laura, Lainie's interim boyfriend Chris, played by Marc Blucas, makes little impression beyond being utterly normal.
Sleeping With Other People seems like the best possible romantic comedy for the present era, a statement that is about 90% of a full compliment. A strong cast, witty dialogue, actors with actual sexual chemistry, and a director with a head for intelligent setpieces is a lot to ask for in something like this, even while some aspects have had the piss taken out of them by detailed spoofs. Headland's film is unquestionably appealing, with enough novelty to put it in the upper echelon of its genre compatriots, but there is a personal ceiling on that genre that those strengths don't quite penetrate.