The latest version of Debian 7 comes with prebuilt Guest additions. This means, when we install Debian 7 on a VirtualBox, it will automatically supports full screen and seamless mode. We don't have to install Virtualbox Guest Additions manually.
Debian 7 has a modern desktop which integrates Gnome Shell. Debian 7 is not an old fashioned Linux anymore. Many new packages and software have been included on the release. Its a ready to use Linux distribution. I have written a simple and step by step tutorial on how to install Debian 7.