I do like the Evil and Kleptomaniac traits, but I don't use them very often. More often than not, I allow the game to pick the traits anyways. That element of chaos just makes things that much more fun for me.
Likewise, I rarely use them together if I
am picking traits myself. Evil has no real benefit for a sim that I want to be a Klepto, and Klepto has no real benefit for a sim I want to be Evil. There is the money benefit, but low finances is a fleeting problem.
When creating a sim, I work out how they work by randomizing the face until something strikes me. Then I tweak the features until I have something that appeals to me. By the time the face is done, I usually have a personality worked out in my mind and I use the traits to bring that out. Thus, I don't bother with gratuitous traits simply because I think they fit together well. I usually need the slots to make the sim who I want them to be, anyways.