FYI to those who are not command-line savvy: When you enter track/artist/other names in this app, precede any spaces or special characters with a backslash (on Apple keyboards, this is the key above the Return key). Of course, you'll also need to remove all spaces and special characters from your file name before you begin. Additionally, it's best to open from and save to your Desktop, so there won't be spaces in the path. These things should help.

To the developer: In a future version, you can fix the first part by automatically inserting a backslash before all non-alphanumeric characters that the user inputs. If you can't figure out how to do that, you can just insert a backslash before every character input by the user... dirty, but in theory it should work as well.