I'm in a union (pension, can't give it up) and I work F/T for one of those flat hierarchy startups, hired through a who's hiring post a few years ago. I actually prefer the union environment even with it's many problems to having no boss which is my other job. I now have to often depend on flaky coworkers who disappear days at a time or spam me with memes all day on Slack, and careless commits I have to fix repeatedly even after telling them the problem each time. There's nobody for me to complain to since we don't have a boss, there's an absentee founder somewhere and just every remote worker for themselves.

The problems with a union is of course your dues being misspent on administrative bloat, campaign donations, executive travel (go to any union site and click on events, there's often 2-3 a month requiring travel), and education costs for executive members. The actual organizers and shop stewards aren't paid anything by the union, it's the top tier executives that pocket the dues. What we tried to do was get them to take half for admin bloat, stop the campaign donations nonsense, and put the rest into a strike fund to pay us during lockouts something more than the picket line pay which is a paltry $100/week. There is typically 4-6years between contracts, and we each pay them $162 a month in dues.

Another problem is of course the adversarial situation that will inevitably become your daily workplace. Your management is now the enemy, as they will never capitulate to all your demands during collective bargaining so every single work meeting you have with them is usually a fight. Everything you do is now paid in time values, so if they ask you to do something that isn't clearly spelled out in the collective agreement you don't do it because it's free work, such as asking your contracted plumber to mow your lawn. This creates many problems, as management repeatedly tries to implement ridiculous new procedures that of course add time which is unpaid.

The positives with a union is you can directly confront coworkers if you have issues with them that are work related (and not criminal such as sexual harassment), so you don't have to go to management which could have them fired. It's nice to work out petty disputes between a floor steward and your coworker without the heavy hand of management adding complexity and fear into the mix. Another positive is you are free to speak your mind directly to management without fear of being arbitrarily terminated or screwed with. It's common where I work to see somebody walk up to management and tell them their attitude is disgusting to their face in front of everybody. Finally you get to bid on everything, so the founder's cousin who started yesterday doesn't get priority vacation over you.

Also goodbye implied forced Christmas parties, implied forced picnics with some visiting sales manager or your boss on the weekend or forced team building clownery outside of work hours, fake vacation policies that claim to be 'unlimited', unpaid overtime, and idiotic work environments like cafes or bars, my favorite idiocy being a historic theatre sized bank building converted into a very loud cafe with wood benches roped off where everybody was expected to work.