What are the benefits/detriments to graduate students joining unions?

I went to graduate school in mathematics at a university with a TA union. I think the main effect was to level off graduate student compensation across disciplines -- so, the union was apparently a great boon to those in the humanities, but I heard that compensation for math TA's would likely be higher if not for the union.

Another benefit to the union was that it instilled (for many) a sense of camaraderie and common cause. Union events were fun, and they served beer. It was a good way to get to know your fellow graduate students.

The main disadvantage was that dues had to be paid, around $200 a year (most of which went straight to the AFT). This is not a lot, but on our salary it did mean something. Dues were mandatory, even if you opted out of the union -- although state politicians have since seen to it that this is no longer true.

Another potential disadvantage is that union dues went (in part) to political contributions to union-friendly politicians. I didn't mind, but this tended to alienate graduate students who were more politically conservative than me.

There was occasional heated rhetoric when I was there, and even more after I left, but overall the union didn't seem to do much good or harm. Mostly, I remember the beer.

I don't have first-hand knowledge of specific details, but I am aware that at my university the graduate student union has successfully negotiated items like:

• Basic health care coverage for GAs, RAs and TAs, with full coverage provided to 0.5 FTE assistants.
• Tuition payment deferment so that earned stipends can pay tuition fees not covered by tuition waivers.
• Paycheck deductions in installments for parking permits for graduate assistants.

I have also been told that they negotiate assistantship salaries and minimum and maximum working loads for assistants, and that the union will represent assistants should a grievance arise.

I've never discussed the graduate student union with anyone in my department – professors and other students alike – and am aware of no negative impacts of my membership.

I was a postdoc at an institution with unionized graduate students. One specific consequence was that graduate students weren't allowed to ever lecture in place of a professor.

This is an annoyance to the professor, but more relevantly, it's a mixed deal for graduate students. When I was a graduate student, getting the chance to lecture was an opportunity---at some schools it's one of the few chances to get that experience while still in grad school. On the other hand I have heard stories (in other fields) of professors abusing this and passing a large part of their teaching load off to their grad students. (This, I assume, is why the rule was negotiated in the first place.)