Give us the option to consolidate/merge history steps.
All the little adjustments with the crop tool (it's often impossible to reach the final crop in a single operation) could be flattened to a single step, all the little stacked basic adjustment tweaks (+5, -7, +3, yada, yada), all the individual brush strokes, etc. could be flattened to a single adjustment.
This would make the history considerably cleaner and simpler - which makes much better use of the limited screen space (scrolling back down through presets and history is a pain).