So much anticipation...
My feelings on the union movement are fairly well know, and my feelings on the behaviour of many of the unions in the UK certainly are. Unions are frequently unreasonable, irrational and short-termist, and frequently seem to spend their time protecting the stupid, the lazy, those who don't really want to work, from being treated any differently from the best worker in the business. Perhaps it's the socialist roots of many of them, I'm not sure.
I'm on record as saying that I would like to see strike action result in damages, following an impartial assessment of which party is being unreasonable, because striking, to many unionised workforces, appears to be nothing more than a blatant bullying tactic to which the employer and the customer has little defence. The history of union bullying and harrassment of those who do not wish to strike doesn't help their case (and even today, my mother in law, who is a union rep, has gone on strike solely because of this demand for solidarity, irrespective of how stupid she believed the reason for the strike to be.
The real problem though, is that it doesn't have to be this way. There is enough protection within employment law that employers can't really screw over their employees any more, which is why union demands have become more and more irrational (eg the CWU postal strike, against the fact that RM are trying to drag the service out of the 19th century, or the FBU strike over the fact that firemen were going to be expected to actually work the hours that they are paid for). Unions have fallen out of favour in most competitive industries because they are damaging to their members prospects (see MG Rover and the refusal to modernise that led to BMW selling it), and now mainly remain in the public sector, and in former public sector, low competition areas, where their behaviour has less commercial impact (and therefore less employment impact) because the customers can't punish the company the same.
What is needed is for the unions to grow up, to move into the 21st century, and start working with employers, rather than fighting everything they do. Actually try looking at the facts, looking at the needs of the business, and then working out the best way for employees to provide that need, rather than ignoring the need, or demanding that the customers have to adapt to the wants of the employees. Where I work, We have an internal staff working group that does just this, and it is very effective in managing the two and getting the best deal for the employees without damaging the business (which will, over time, lead to redundancies). It works because the members all have an interest in seeing the company do well, something that is sorely missing from the modern trade union (which is a business in itself), which is more concerned about raising it's own revenue than anything else.
Are unions a force for good or evil? the idea is neither, the reality depends very much on the union and the business in question...