Are there reasons for leaving that I should not mention in an exit interview?

Do not be overly candid in your exit interview. The interview will be saved as part of your record and can be accessible if future employers contact the company for a recommendation. You can mention whatever incidents you feel comfortable sharing, but don't bring up personal grudges or perceived personal injustices. Keep your comments to basic office procedures that you feel detract from the work environment or reasons you're taking another job, like a better salary or a better chance for promotion. You can usually safely talk about your manager in a work performance sense, but do not bring up comments about the manager's personal flaws.