No I actually cannot play back yet. But it's not hard to implement, it even would be relatively easy to selectively play back only certain edits. I believe in the worst case a few thousand edits would suffice (though it would be rather tedious on the keyboard to do: type - then go back one with the arrow keys and type again).

Collabedit looks nice and solid! (Hadn't been aware of it.) Did you roll your own editor or did you use something like ACE or CodeMirror?