You are right. In the old version of Sitefinity you did not have to do anything in order to setup a panelbar navigation control. In the new version though, the datasource for the panelbar is not set automatically and you have to do it manually. For the purpose, drop a SiteMapDataSource control on your template and set its ID property. Then drop a radPanelBar control, click edit, and in the Data section set the DataSourceID property to the ID of the SiteMapDataSource you have specified. This should work for a one-level page hierarchy.
It does not display child pages, though.
If you want to display a hierarchical view, the only way to do it with panelbar is to create a user control containing the panelbar and do the logic in code, but I suggest using another control for navigation.