I follow Kevin Drum in my general attitude to unions: they're a necessary part of the republic, but they have their problems like other parts of the republic. I was in management when ASCS employees in DC voted in a union. Managers got some orientation on how to deal with the union. The bottom line seemed to be: do what you should have been doing all along. That is, document poor performance, consult with employees on what you're doing, etc.
Of course, federal employees can't use unions to bargain over pay. I've forgotten most of what I once knew about the laws and regulations. It seems, though, Wisconsin employee unions could bargain over wages. So in one sense, what Gov. Walker is working for is to make those unions as powerless as federal unions, not that that's very obvious from the discussion. The big difference I can see is the requirement about voting for the union every year. That's really critical. I suspect the reality of unions, as for other institutions, is many members lose enthusiasm after time. So inertia takes over. People go with what's easiest.