My wife is a food+drug union worker in California. The positive side is we have excellent healthcare benefits. The negative side is it breeds incompetence/laziness? on all levels, from the union down. If you've ever dealt with a troublesome HMO, just wait until you deal with a union, if you can even get a hold of anyone that knows what they are doing within it. In addition, since it is quite hard to get fired most of the employees take advantage of it. The customer service difference between Safeway (union) and Trader Joes (non-union) is astronomical, and Trader Joes even pays more than union wages.
I'm not anti-union in general (I did mention great healthcare benefits), but they definitely have consequences.