Surely the most basic test of the value of unions is the levels of membership where its voluntary? In Australia only 14% of private sector employees are in a union. That about sums up what most people think of them.
One thing that seems to be ignored sometimes is the implicit pact for public sector workers - generally lower wages than their private sector counterparts, but in return the expectation of pretty secure post-retirement lives. In any event, if governments start to change this pact they need to give people serious lead time to self invest - at least 15-20 years if you expect somebody to seriously contribute to their own retirement.
Sometimes the unions themselves have broken this pact. In the public sector in Queensland, public sector unions (which basically run the Labor party here) have routinely had wage rises above inflation irrespective of any improvements in productivity. As a result people in general office jobs here for example earn far more than they could if they left the public sector - ten years of inflation plus 2% will tend to do that. That in turn leads to bloated public sector costs and huge inefficiency relative to the private sector. Bizarrely the very same unions that have forced these wage rises through then complain bitterly when the government is forced to look at provatisation to balance the books.
One thing everybody should look at when planning for their retirement (if they have the ability to do so - most funds worth their salt will enable you to do a bit of diversification in a general sense) is to try to diversify some of your investments. The sharemarket is always a bit of a rollercoaster, and whilst returns over the long-term are generally good, you can face significant short to medium term volatility in the value of your shares - a real problem if you face retirement on a maturing investment during a sharemarket collapse. I know quite a few older people here who are really worried about having to postpone their planned retirement as they simply cannot afford to stop working.