We all love the dog, except when he needs a bath. Same with interviewing. I have conducted countless interviews where things seemed to be going just fine, when the interviewee began a series of complaints about others. And the spotless interviewee has suddenly become hopelessly stained.
Is there anything worse than a complainer? Nope, nothing worse. We all know one, and we all want to distance ourselves from that person. Company or otherwise. So remember that the interview is not your forum for griping. If you gripe about your current or past employers or professors or make note of any shortcomings in your life of missed expectations (even though they may be few!), you have just relegated yourself to the position of "complainer." And complainers are all too common already within most companies. Why would any company hire new complainers? They won't. Be positive about everything. Case closed.