For organizations using various Atlassian products and dealing with multiple user sources or directories, implementing Atlassian Crowd for single sign-on proves highly beneficial. This is especially true for companies that have instances of Atlassian product installations across different entities, each with its own Active Directory and user directory. Crowd significantly streamlines user and directory management, making it more efficient for larger enterprises. It is particularly advisable and recommended for big companies, especially those that have undergone acquisitions or mergers, as it enhances user management, transparency, and configurability. While it's incredibly useful for enterprise-level businesses, it may also be suitable for mid-sized companies with a substantial user base. Overall, I would rate it nine out of ten.