We've migrated several customers to Atlassian's Cloud. Many customers want to have a pure SaaS offering, whereby they do not need to run any systems at all, but simply consume the service. Here are some of the lessons learned.
confluence
Are you a Confluence user? If so, you should be aware that Atlassian have today announced two critical security vulnerabilities (both Server and Data Center versions but not Cloud).
Confluence, Atlassian