I went from union to non in the same company last year and it's a pretty stark difference. There are a ton of people who refuse to talk to me as a result.
The good news is that they are mostly the people I don't want to talk to anyway, so it works out fine for me. They are also the same people who refuse to talk to management for any reason because "fuck management," so now I get to occasionally say "Well, I could have helped you out if you had brought this to my attention earlier, but you didn't, so now, per the rules, we need to go this direction. Take it up with your union."
It's good times.