My dad is, or at least was, anti-union. He worked for a major car company back in the dizzle, and his experience with unionized workers was negative. He described them as holding the company hostage, basically working all day with the implicit threat that they would all go on strike if they didn't get their way. And "their way" involved being lazy, disrespectful, and doing as little as possible.
While I completely believe that this was the case (because my dad is many things, but not a liar), I generally disagree that unions are just plain bad or just plain good. I believe that in the economic climate of the time, the workers didn't feel a sense of urgency or loyalty. If the success of the workers was more directly tied to the success of the company, that would probably have been all the incentive they needed to work hard every day.
I also recall a story on NPR (one I've been unable to verify myself) a while back that said, in passing, that the starting wage of a general labor job at a major American car company is $40 an hour. If that's true, it is ridiculous. They're necessitating their own layoffs; the labor union is pricing its members out of their jobs.
All of that said, I support any organization that stands up to The Man. Srsly, fuck that guy.