Visibility groups are too difficult to use. Setting visibility on each item is not realistic, and becomes impossible to manage once you have 2+ people with limited visibility making changes. Plus it is tied to Pipedrive's more-expensive plans.
It would be really great to have a feature that ties visibility to specific Pipelines. Our situation is that we have a couple 3rd parties we work with on recruitment (sales). We don't want to give them access to all of our customer history in Pipedrive, but we do want to give them access to a couple Pipelines and their associated Deals. We are happy to pay for the seats, that is not the issue! We just want to be able to work collaboratively with these folks in a limited capacity within Pipedrive.
I'd love to explain this more to a developer and see if it could be implemented in the future.
Having a "Guest" user type might be necessary, too