Somebody must have already mentioned this (I didn't read all the messages above): 1. It's probably too late for CL to add the "multiple undo" feature to P6. They are already planning what to do with P7. 2. If they do decide they have the budget to add the feature to P7, any use of "multiple undo" will be a far worse RAM hit than the memory bug that affects complex scene renders. 3. If they try to make "multiple undo" a read/write function to scratch disk, this will slow down the Windows version quite a bit, and will probably kill the Mac version, which already has severe problems with excessive page-outs.