Steve Carell is just fine as the cuckolded dad, who's never had to romance a woman in his life. He wears baggy khakis and New Balance sneakers to dinner- I normally would call this "I surrender", but marrying your high school sweetheart means you never had to try in the first place.
Julianne Moore is his wife, who's having a much-deserved midlife crisis after 25 years with her high school sweetheart. Her part is a bit underwritten- there's one scene missing that justifies why she point-blank wants a divorce. She has a fling/affair with colleague Kevin Bacon, just slick and smarmy enough to gross us out.
Ryan Gosling is funny as the charming Lothario who respects all the beautiful women too much to play games with them. Emma Stone is a perfect foil for him, they work very well together. The culmination of their romance is both surprising and organic.
I simply loved Marisa Tomei as a single lady out for a good time. When Carell completely botches his sloppy attempt at picking her up, some kind of reverse-lock takes effect- the same kind of surprising but organic relationship. Also, when her character finally goes off the rails, it's electric- I remember why she won that Oscar for comedy way back when.
Analeigh Tipton is perfect as the gawky, overdressed teenage girl who has a crush on Carell, but is pursued by Carell's son (Jonah Bobo, perfectly cast as Carell and Moore's offspring)
My wife thought this was based on a French comedy-- the slapstick third act certainly feels like it-- but it's credited to Dan Fogelman, who wrote three animated movies before this (Cars, Bolt, and Tangled) and has since created the aliens-in-my-subdivision TV comedy The Neighbors.
Steve Carell is a comedy genius - under-appreciated for his work on The Office - but his movie choices have been uneven. The Forty-Year-Old Virgin is brilliant, Little Miss Sunshine is very pleasant, but Get Smart, Dan In Real Life, Evan Almighty, Date Night, and Dinner For Schmucks are all lukewarm at best. I also believe that audiences are more reluctant to spend money to see a TV star in a feature film. The thinking goes- "I have seen Carell on The Office for free for six years- why should I pay $12 to see him act goofy in a movie?" This is why I have yet to see a Tina Fey movie in a theater, while I have seen every episode of 30 Rock, many of them twice. The good news for Carell and Fey: our standards our lower for renting a movie on a Friday night.
My wife saw CSL with her lady friends in the summer of 2011. In the summer of 2011, the TV commericals made CSL look like another formulaic rom-com, much like the other two rom coms that year, No Strings Attached and Friends With Benefits. Turns out CSL is a thoughtful, nuanced, intelligent comedy (with a wacky streak) that happily surprised me 18 months later, watching my mother-in-law's Netflix DVD with my wife and sister-in-law.
NOTE: both of those rom-coms co-starred That 70s Show alumni -- Ashton Kutcher in one, and Mila Kunis in the other. At the time, I tweeted:
Every cast member from That 70s Show is doing one. Next up is Topher Grace & Jessica Alba in "Fuckbuddies!"