I am not sure I get the appeal of this app. If you are this interested in network security, you'll probably already have a robust firewall for your entire network and this would be mostly redundant.
Most people don't understand what a firewall is, let alone how to configure a "robust" one.
Little Snitch gives you an application level firewall that a regular, non-technical user can understand.
As such, it may be pointless for someone with your technical expertise, but it's great for regular folks like me.