Advantages to this approach to referring to an older version of code that alternatives may not have: * works well entirely through keyboard shortcuts (especial

Advantages to this approach to referring to an older version of code that alternatives may not have: * works well entirely through keyboard shortcuts (especially useful when editing code) * the shortcuts are standard so you already know them and have them committed to memory * works across editors * high granularity of control over exactly which version of the old code to refer to Undo trees seem like the best alternative, since it can be done strictly as an extension to convention undo/redo... a little HUD can let you see your current location in the tree and the normal keys can be used to navigate it, with the addition of one more shortcut to change branch. The "separate window with panning control" suggested in the article seems awful to me.