...
A workflow condition that enforces separation of duties (for SAS-70 70 compliance), i.e. that makes sure the same user cannot trigger two incompatible transitions on the same issue.
For example, you can prevent a user who has triggered the "Resolve Issue" transition on an issue to trigger the "Close" issue.
...
The Skip if Assignee option allows you to prevent the automatic assignation to the role member if the user specifies an explicit Assignee in the workflow screen.
Assign to last role member (new in 1.2) (updated in 1.5.1 & 2.4.1)
A worfklow function that assigns the current issue to the latest Assignee (excluding the current one) who is a member of the specified project role.
When the function is executed it goes backwards through the change history of the issue. When it finds a user that belongs to the specified role, it assigns the issue to that user. Optionally, it can consider the Reporter and/or the Current Assignee in addition to previous assignees.
...