Owen,
I have this utility too; it does use ExifTool as its "engine".
The first is a very fine program called Exiftool (currently at version 8.28) which allows all sorts of clever reading and manipulations of the .jpg file header information.
Not only jpegs, tif's & raw files too. Fortunately, ExifToolGUI creates a backup as default.
Terry
Yep, ExifToolGUI is handy. You can't edit ALL fields, as I assume you can with ExifTool itself, but it's all I need at present. The default backup is indeed a convenient feature.
Ditto for the "All Metadata" option under "Remove." Have you seen the recent news stories about people who have unwittingly revealed their exact location by innocently posting photos from their brand-new GPS-enabled camera? A great way to reveal to the world exactly where you're getting all of those great shots of unspoiled nature, wildlife, etc. And as a matter of safety, I guess it would be okay to post a picture of your new and expensive flat-screen TV to your Facebook page, but stripping the GPS metadata before you post might be a good idea. Modern life.