After using Emacs' wdired for some heavy-duty work, I noticed a flaw in how it does renaming.
Some background for those who do not know what wdired is (I find it indispensable!): wdired gives you a view of a directory that looks like the output of ls -l. However, you are allowed to edit the filenames. When you "save" the buffer, wdired renames all the files whose names you have changed. (More information: a blog post about wdired; Emacs manual node for wdired)
Here's the problem:
wdired always performs renames in a fixed order, starting from from the bottom of the buffer and going up. You can easily construct sets of renames where wdired unnecessarily thinks it has to clobber a file because it is doing the renames in the wrong order.
I improved wdired-finish-edit so that it does renames in the "right" order. I've posted the improved version on my web site.
While this does complicate the implementation a bit, the apparent model that wdired presents is that all the renames you ask for happen simultaneously, so I believe there is no reason when this new behavior would be inappropriate, assuming the code is not buggy.