So far we're using them in projects to represent the resource type most likely to be involved in a task, as both as a "prior to assignment" mechanism to make it easier for team members to grab tasks for themselves and for the team/PM to recall what type of resource was going to do the work... and then during in-progress, the usage shifts to enabling the PM to filter or group based on the same to have more focused conversations with those resource types / their managers about what their work is... But, certainly sometimes we have more than 6 types... and I can't say we landed on saying that's what we're always going to use them for.
If you are using this tool as a Kanban / SCRUM team, I think these are great for assigning agile point values. Name each tab as an ascending value from the Fibonacci sequence ( 1,2,3,5,8,13), then you have a one-click way to assign estimates rapidly to a set of stories / tasks. The only challenge is in reporting. Because the label attribute is a multi-value field, it isn't exposed yet to other solutions like Flow. That makes it difficult to pull data out for reporting purposes.