One of the only movies ever to make the killers fully dimensional characters(for the most part)and also have them be the main characters. As many people have already stated, it's emotionally bi-polar as one minute something horrific is happening and you feel bad, and the next minute you're really enjoying the characters comitting horrible crimes.
You grow to really like the characters which is really confusing, Bill Mosley does a fantastic job as Otis, and i'm sure everyones favorite is Sid Haig as Captain Spaulding who is the funniest (big suprise, he's a clown) But the person who falls the flattest is Sheri Moon Zombie as Baby, who is just kind of annoying and i find her the least interesting. Overall I don't hate her she just dosn't do as good as the other two.
By the end of the movie it's very suprising how emotional it makes you feel when the three die, as Free Bird plays in a very epic scene. Even though they deserve to die you feel a hundred times worse when they do opposed to when they murder all the innocent people.
All of that may have to do with the fact we get to know them better and they're funnier, but it's not like the people they murder or the worst characters either we get to know them a little bit and they arn't just annoying teenager like in most horror films.
I would definatley recommend it to those who like dark humour or just horror movies in general. (don't bother watching house of 1000 corpses)