file renaming is old technology, this niche market is crowded, and each and every app out there competes on the exact same features: I'm the fastest, I have undo, I use drag n drop.
Strainer is more than that, its better than every other file renamer. Better because it was designed to do what you want done with less setup, less effort, and less UI.
Strainer maintains a list of search text and replacement text. As your needs grow you can add to this list. Strainer then uses that list to fix the file names of files. Because the list gets bigger, Strainer gets better at fixing file names, and in one step you can do a whole lot more work than would be possible with any of the other solutions out there.
The interface is small, so it gets out of your way quickly, unlike the other guys, who fill your screen and force you to go through multiple steps just to get file names fixed.
oh, right I almost forgot... strainer is also the fastest, it supports unlimited undo, and supports drag n drop.