I normally use WildRename to rename batches of files and have always found it very effective and reliable, when it renames files it first places a simple text file [_wildrename_undo_.txt] in the directory containing all the original and new filenames so it can very easily undo all the changes it made, just in case.
I think the renaming option in MC is great and touch wood haven't had any problems yet but I though i'd mention it as it seems a very simple method of undoing a rename job just in case the worst happens.
Thanks