I put this second version of "The Man Who Knew Too Much" to my Top 10 Hitchcock movies. Together with "Frenzy", it's probably the most argued film among the fans of Hitchcock. I consider it far better than, say, "Rebecca", which has gained unreasonably much appreciation.
The film contains many ingenious scenes (most of them have been mentioned in other reviews), but that's something to be expected from Hitchcock. It takes almost half an hour until things really start to happen, but that time is used for preparing the following happenings, which are full of intriguing suspense.
If you can ignore the clumsy rear projections, the only weakness of this film is the main villain, played by Bernard Miles, who is a rather flat and undeveloped character. Luckily, there is a creepy assassin in the form of Reggie Nalder. And Hank, the little boy, isn't as irritating as most kids in old movies.