From the pont of view of a member of the audience, I sometimes welcome the crappier slots because it gives me a smoke break and a chance to empty my bladder and refill my glass.
At one club I know there's a very nice chap who sings the most dire songs of his own composing (with, it has to be said, a superb 12-strong accompaniment) who prompts a Gadarene rush to the bogs whenever he comes up to the front, and who is often drown out by the squeak and squelch of the beer pump!