The film feels like a throwback to those continental heist pictures of the '60s, filled with impossibly sophisticated characters and exotic locations. There are also very funny moments of low humor, especially involving Martin's unforgettable impersonation of "Ruprecht the monkey-boy". Although Martin is at his comic peak here, Michael Caine very nearly steals the film from him, as the suave, elegant crook -- the kind of role that David Niven specialized in years earlier.* It's great fun watching them match wits, trying to one-up each other in surprising and unexpected ways. Oz has to be given much credit for keeping the proceedings reined in enough that they never go too far, never disrupting the tone or style he has achieved so well. His impeccable gift for directing comedy has never been better served than it is here. Certainly one of the best comedies of the decade.
*Upon further research, I learned that this film was indeed a remake of a 1964 Universal comedy, THE BEDTIME STORY, which indeed starred David Niven in the role played by Michael Caine here.