I've been part of two unions as well, and while the last one - District Council 37 - was more or less useless, it was mostly due to ineffective leadership and a too widely disparate rank and file to really be organized in an effective manner. The other had a far more effective means of collective bargaining and also knew how to use allied unions to rally for a common cause.
The thing is, pointing to bad or shortsighted leadership within unions and thus saying "we don't need unions" is, in my opinion, throwing the baby out with the bathwater. Bad leadership is bad leadership, and if you read my blog you'll see plenty of examples of bad union leadership, but no representation is far more of a detriment to labor and society overall. I am most definitely a universal supporter of unions because they need to exist. They should exist with competent leadership, but first and foremost they need to exist.