If you don't have plans to see this movie, you can check the spoilers here and then come back.
Just not good. The plot was lame romantic comedy fodder--two friends decide to "just have sex" but fall for each an hour and a half or so later--but not irredeemable with a better script, which this did not have. Almost every line spoken by either of the main characters was some sort of sarcastic snark to the point where I was just angry at them. Justin Timberlake and Mila Kunis are among the most likable performers I can think of, but in this film their characters of Dylan and Jamie are just irritating. It doesn't help that both leads seem completely unmotivated for the most part and deliver said crappy lines as if they're reading off cue cards. There are rare moments when they pick up a gag and make it work that had me mourning for the potential of this pairing if both were performing at 100%, but a lot more where I just wanted them to go away. The highlights are the supporting turns from Patricia Clarkson as Jamie's hippie mom and Woody Harrelson as Dylan's freewheeling gay buddy plus a great cameo from Emma Stone having more fun than anybody else in the cast, but Richard Jenkins, Jenna Elfman and others who should be better just whiff. With this cast, even a flimsy premise should have potential, but they came off as if the script had beaten down any enthusiasm they might have had, and less then 10 minutes in I felt the same way.