How often will you be doing this kind of renaming? My favorite quick'n'dirty method for mass approval is to dump everything out to a file in the form of pairs (from, to), then edit the file with a text file -- deleting lines I don't want there -- then using the file to fire off the actual renames. This can be accomplished by simply inserting the string "mv " in the beginning of each line for simple cases.

Not offering this as a programmatic tip, but as a pragmatic one for certain cases.