The Ladykillers is about as bad as the critics say. I was disappointed, since Tom Hanks' over-the-top character work had me very excited about the trailer--easily one of my favorite trailers of the year. But it turns out I missed little by skipping the thing in theaters. The best lines are in the trailer, and the added context of the story only saps them of their bizarre energy.
The one laugh I got came from a scene in which Hanks, a con man posing as a professor, hides under the bed when the landlady, Irma P. Hall's character, tries to introduce him to the sheriff. After she finds him, Hanks explains that academics enjoy stuffing themselves into confined spaces--a hilariously idiotic lie which he proceeds to justify by pointing out the popularity of phone-booth stuffing on college campuses.
Aside from that, not so funny. It mostly consists of moments where you feel you're supposed to laugh, but don't really want to. The Coens are struggling lately, between this and Intolerable Cruelty. While they're known for dark humor and contemptible, unlikable characters, they might do well to avoid films where practically everyone falls into that category. Since they lean in that direction to begin with, it helps to have someone likable to temper it. Also, the broader comedy in this and Cruelty doesn't gel so well with their black comic sensibilities. O Brother was broad, but somehow had much more command over its tone.