I heartily agree that unions have helped with "safer working conditions, weekends, paid vacations, sick leave, and a host of other things ". However, they have also failed miserably when it comes to things like nonsensical work rules, seniority, and protecting useless workers.
The one example I can give is my first job (which was a union posiiton). There was a guy who used to hide in the toilet to read the paper or sleep. There was another guy who ran a vitamin supplements business from his desk. They were useless workers and yet every year we got the same pay raise. Management (also useless) tried to get rid of them several times, but the union reps always managed to save them.
In an ideal world, I would like to have the benefits that unions have brought without the the soul sucking lowest common denominator mentality that holds back conscientious workers.