What most people not realize is that a GUI root login is not only dangerous for your machine, but can also be very annoying and dangerous for other people and you.
Imagine this one case: You are logged in as root and a problem occurs, where you have to do a web-search for solving the problem. Do you logout and login as unprivileged user for that? Or du you start the browser as unprivileged user? In most cases you won't, I bet. So you are exposing a system whith a browser running as root to the web. A simple unpatched exploit and your system belongs to someone other. And that other person can do very annoying things: Send spam, use your system for brute force or DDOS attacks, steal your data (online-banking, ebay account, etc.). And he can do more illegal stuff, that also can bring harm to you, for example hosting child porn on that machine.
So running a complete GUI as root is never a good idea. If you need a file-browser as root, start the file browser as root. If you need a different tool as root, start that as root, but never the complette GUI.