Date Night is a harmless bit of adult comedy that, although written by Josh Klausner, is a perfect copy of the style of Tina Fey's brand of humor. Unfortunately, here the comedy is hit and miss and the saving grace is the underlying message of a middle-aged couple that are comfy in their lives, while wondering where the passion has gone.
What works here is the chemistry between Steve Carell and Tina Fey; you really seem to know this couple and root for them, even through some rather absurd comedy sketches that have a "knowing smile" factor while going wide of the mark on laughs. But the chemistry works really well - and is a necessity in this type of romantic comedy. Taking for example a similar type of film, The Out of Towners, you can easily see the difference chemistry can make - Jack Lemon and Sandy Denis had it, and the remake did not.
The story of the film is the old saw of mistaken identity, and while director Shawn Levy does a nice job of keeping an even pacing, the plot's implausibilities weigh the film down, making it obvious that this is intended as a comic vehicle - an unfortunate choice as the film, quite frankly, isn't all that funny (all the really funny lines were left to the outtakes that rolled over the ending credits - most of which was riffing from Fey).
The acting overall is fairly good, with a shout out to James Franco and Mila Kunis who shine in their brief time on screen as Taste and Whippet, the "other couple" that Carell and Fey get mistaken for.
The final analysis is that Date Night works as a light comedy of a couple of a certain age, dealing with kids and jobs and not having enough time to be more than, as one character puts it "really good roommates", but as a laugh fest it falls well short.