Cary Grant's charm and charisma could make almost anything watchable, but this is a very good film with good, snappy dialogue. Still, the second 'weepie' half is not as good as the wise-cracking ocean liner-set first half, and there's far too much singing by those sickly children, which has me contantly reaching for the remote to turn the volume down.
Also, that bit where they leave the old (but how much older than Grant!?) grandmother in Europe, and you just know that this is going to be the last time they see her, is much more sad than the tragic accident and failed meeting atop the Empire State that it precipitates. When Kerr starts humming to the old lady's piano I started to cringe, but the scene turns into something quite touching, probably due to the superb, subtle perfomances from all three actors in it.