The following are features that really set it apart from all other file encryption tools, commercial as well as free:

• Double-click to edit/view with any application.
• Automatic re-encryption after modification.
• Absolutely no user configuration necessary or possible before use.
• Open source under GNU General Public License.
• 12 languages in one executable distribution.
• Extensive command-line interface for scripting and programming.

• Windows 2003/XP/Vista/2008/7 32- and 64-bit compatible.
• AES encryption with 128-bit keys.
• Edit an encrypted document directly with double-click.
• Optional pass phrase cache - type pass phrases once per logon and/or reboot.
• Automatic pass phrase validation before decryption or editing.
• Key-File generation and support.
• No options or user interface - easy to install and use.
• Relatively light-weight, less than 1Mb download
• Extensive command-line interface.
• Server mode options.
• Support for files larger than 4GB (except for self-decrypting files).
• Dynamic brute force counter measure - iterative key wrapping.
• Integrates well with web based file sharing services.
• Selective compression before encryption - faster downloads/uploads.
• Retains original file name and information of an encrypted file.
• Integrated shredder.
• Shredding of all temporary and encrypted plaintext files.
• Secure memory handling - no keys or data in the paging file.
• Industry standard algorithms.
• Data integrity verification - no undetected modification.
• Unique data encryption keys used for every file and (re-)encryption.
• Easy to add more languages - contact me (I'm especially looking for Nordic languages)!
• Open source - no backdoors.
• Private branding support for commercial or corporate versions.
• It's FREE!