If I go to the System Preferences and select iCloud, it prompts me to sign in with my Apple Id. Only problem is, it auto-fills the Apple Id of the previous user. If I try to delete the existing id by clearing it out, it comes back the next time I bring up this panel. This seems like a serious information leak, I have no business knowing this info, and it does not inspire confidence that all traces of the previous user have been removed.
When I look at my dock, the FaceTime app currently shows a number "7" in a red circle in the upper-right corner of the icon. If I open FaceTime it prompts me to sign in to "activate" FaceTime, but if I long clicked on the icon, I see "recent calls" of the previous Apple Id. Again, this isn't something that a new user of a computer should be able to see.