Dragging in and out doesn't seem to be working for me, but I can see the ones I dragged in there before I upgraded:
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You should still be able to drag items on to the sidebar. To remove them either right/command(⌘)-click and select Remove from Sidebar or drag while holding ⌘.
I don't think you can drag folders out anymore (to prevent accidental deletions), but if you right click you should have a "remove from sidebar" item in the context menu.
Command/drag works for me - as does the right click.