How others will see it. Guiness wears makeup that makes him look ghoulish, almost like the phantom of the opera without the mask. Aside from his odd appearance, this film should be a delight to all forms of droll English comedies. The fact it is in color doesn't make it any better, of course, but it does make the film more acceptable to a 'modern' audience. The English accents, however, often require concentration to follow the dialogue.
Peter Sellers has a relatively small supporting role, as one of Guiness' gang. His character is also a bit flat. Fortunately, the other gang members have distinctive and amusing personalities.
How I felt about it. The English have a more whimsical sense of humor than Americans. Comedies based on crime are not as popular on our side of the Atlantic. Some Like it Hot is slapstick, and that is the approach an American director (yes, I know Billy Wilder was from Europe) would likely take.
The Ladykillers has its moments of slapstick as well. Particularly, a scene where the clumsy criminals have to chase their elderly host's parrot (or whatever exotic species it actually is). And there is the silliness at the train station, which is the gang's preferred method of disposing of bodies.
But the humor is mostly of distinct British flavour. The police humor the kindly old lady, who is considered senile but is not. Alec Guiness shows knowing patience with his maddening host, who is just enough aware of her surroundings to unknowingly create mischief.
Crime does not pay, particularly armed robbery. We know that the crooks will come to a bad end. The interest is seeing their plan execute and be executed. The story really begins when the deed is seemingly done, but is about to be undone. The twist here is that the crooks are confounded by their sense of morality. Sure, they're highwaymen. But they're simply not ladykillers.