Name Mangler, Many Tricks’ excellent batch file renamer, has been updated to version 3. The new version is much faster and can apparently even undo a renaming, though that should rarely be necessary since it offers such great previewing. There’s also a version in the Mac App Store, which due to sandboxing removes the feature for integrating with Path Finder.
Update (2013-03-01): Peter Maurer:
In this case though, we’ve demonstrated that not only did we not steal, but that any theft may have very well been the other way around: Renamer 4′s “new” interface bears a striking resemblance to one we’ve been using since 2005. But honestly, we don’t care—we like competing on features, performance, and ease of use instead of with legal threats.