Oh. Available next week to First Release tenants. But still, I know what I'll be doing next week... exploring the new SharePoint page features and Group integration.
"When you create a group, Office 365 gives the group a shared inbox, calendar, OneNote notebook, a Planner for task management—and now, a full-powered SharePoint team site. Each group gets a modern home page—with the ability to create additional pages—document libraries, lists and business apps."