All marketing email has an unsubscribe link if it didn't before, and you know it actually works now to stop the emails, not just confirm your email address works.

You also know you can get all the information a company has on you, and get them to delete it if you need to. I haven't made use of it yet, but I've read of people who have.

From inside the business side, I see most companies thinking about GDPR compliance when developing new products and features. What was never the case before and you notice now is they try to minimize PII collected to avoid headaches, and they are very careful about how data is shared with 3rd parties, asking for consent before doing it, etc.