When I have interviewed people who complain about their current or last job and tell stories about how the work is shit and the management sucks I can't help but get the impression that they are a difficult employee. Maybe that's not true, but without knowing anything else it's easy to get that idea. And I would prefer the candidate focus on what they are bringing to my project and team rather than than talking about how their current/last job sucked.
A decade or so ago I worked for a large-ish publishing company. We were hiring a couple of programmers and I was one of two senior people assigned to do initial interviews. One candidate came through a recruiter, looked good on paper, and he had several years of relevant experience at a major publisher (Playboy) using similar technologies. During the interview I asked why he left that job -- he had a several month unemployed gap on his resume. He said he didn't like working in the "porn" industry. I said "You must have known what Playboy publishes when you took that job." Then he launched into a long explanation of how he didn't get along with his manager and how some of the other people on his team were slackers and so on. We didn't hire him -- maybe he was right about the work environment but the whole exchange left a bad taste for me and the other senior doing the interviews.
Bottom line: Prepare for the question "Why did you leave your last job?" (Or "Why are you thinking about leaving your job?") and have an explanation ready that doesn't reflect badly on you, makes sense, and doesn't require badmouthing the last place.
