Based on the 1960s spy spoof series, Get Smart is a fast moving comedy thriller with Steve Carell and Anne Hathaway taking the leading roles. Max Smart is an analyst for espionage agency CONTROL who yearns for field work so much that he has lost 150 pounds and got an A+ on his agent exams. Initially he's too much use as an analyst to be allowed onto the field, but a disaster gets him promoted to partner Agent 99 (Hathaway) as they battle the forces of evil crime syndicate KAOS.
I never saw Get Smart the series, so I can't comment on how well this replicates the original. However, spoof spy stuff is a fairly overcrowded market, from the original Casino Royale  to Johnny English . Even the Bond movies -- certainly of the Roger Moore era -- were as much spoof as they were serious espionage. Add to that Carry on Spying, Austin Powers, The Pink Panther and the Spy Kids trilogy, and a spy spoof has to work hard to be more than temporary entertainment.
Get Smart has some good action scenes, and the odd-couple combination of Hathaway and Carell is interesting enough, but it doesn't compare for humour with the anarchic foolery of Johnny English, and the dialogue slows down for explanations far too often -- as when Hathaway explains to Carell how spy stuff works. Aside from the jokes, the plot is fairly thin.
You may chuckle a bit through Get Smart, but you're unlikely to be laughing out loud. This is one example of comedy which just doesn't make it across the Atlantic.
Verdict: fun enough, but this isn't one of the cinematic experiences which you will treasure for ever.