For a renaming app which relies on a visual interface for its options, this has a huge amount of possibilities, allowing for very advanced combinations.
You can add a prefix, a suffix, insert text/numbers in the middle of the name at the place of your choosing, number files automatically, find&replace text, and much more.
There are a lot of checkboxes, blank text-boxes, and drop-down lists in a single window, and this makes it sometimes hard to notice a mistakenly (un)checked box. Also, this can scare a new user away because it looks much more difficult to use than it actually is.
The order of the rules is fixed, AND all the options are shown in the same window, which results in a horrifying display of nearly 100 options. Compare with Advanced Renamer, where you not only can decide the order of the rules yourself but also can repeat rules. AND despite virtually limitless possibilities, the UI remains clear and pleasant to your senses.
Once this is installed, it takes extraordinary efforts to delete the generated files. The program is easily removed but the dll insinuates itself into your system and can't be removed without manual editing of the registration. Good program other than that but in this day of Cold War renewal, you probably don't want a communist country software burrowed like a tick into your PC.
The order of the rules is fixed, AND all are shown with all their options are shown in the same window, which results in a horrifying display of nearly 100 options. I've known people being hanged for less. A hundred options, and I still easily think of a job you can't do with it. Compare with Advanced Renamer, where you not only can decide the order of the rules yourself, but also can repeat rules. AND despite virtually limitless possibilities the UI remains clear and pleasant to your senses. Frankly I don't get why BRU gets so many upvotes.
You can create your own rename rules with scripting, rename according to CSV lists, rearrange parts of the filenames, edit filenames in the text editor, extract media properties & metadata, such as width/height and duration. It is also possible to extend FlashRenamer with ExifTool for thousands of more properties and tags.
It has many options, including renaming using tags (ID3, Exif...), can number files, use wildcards or regular expressions, walk a hierarchy of folders.
And it has presets for common renaming tasks, like removing parentheses, "Copy (n)" or "Shortcut of", and so on. Its preview feature avoids errors, and warns (a bit late though) of naming conflicts.