Great tool. A weird quirk is that none of the files changed has the modified date changed so I can't tell which files have been changed.
For example I have 1600 images that someone used a space so that space has now been changed to %20 in the actual file name. Maybe 10% of these files have this problem. This tool renames them just fine but I can't tell by looking in explorer which files were changed. There is a Change File Timestamps option but that changes all selected files rather than just the files that matched my renaming requirements.