Pros:
* Makes using Encrypted disk images (dmg) files easier.
* Pretty animations for locking and unlocking of images.
* Allows for management of encrypted disk images you've used.
* Has an "assistant" that can put various confidential info (email, chat logs) into an encrypted DMG.

Cons:
* OS X provides the basic functionality (AES 128/256 encrypted disk images) as part of the operating system. A lot of users will dislike paying for a product whose core functionality is provided for free by the OS.
* While it makes creating and using encrypted disks easier, it's not particularly hard to begin with.
* A fairly hefty daemon that runs even when all file "safes" are closed.
* DMG files created don't appear to be openable using the same password used for encryption. (ie. you have to have FileGuard to open the contents, even if you know the PW)