I can only echo what Lonewolfreloaded said. I have used them in some campaigns I've run and not in others depending on the tone of the campaign. I have played in both games with them and without them. They can add to the game in interesting ways. Most of the cards aren't too overly complex in their adjudication, but there are a few that may make GM's that are a little less comfortable with winging it at the table want to take them out rather than have to deal with them.