Nowadays, it goes beyond of just a fork and adds a lot of new functionality.
Some of the major features you can find are:
* Easy access to remote actions like: push, pull, submodule management and branches
* Branch management
* Tag and stash management
* Submodule handling
* Open several repositories in the same window
* Better visualization of the commits and the work in progress
* Better visualization of the repository view
* Improved UI experience
* Easy access to the main Git actions
* Better code separation between Views and Models
* Simplification of different options, keeping it to what a Git client is ?
suposed to be.