Currently using statements are for namespaces only. With this new feature they can used for static classes as well. Like this:

using System.IO;
using System.IO.File;

namespace CSharp6Features
{
    class UsingStaticClass
    {
        public class StaticUsing
        {
            public StaticUsing()
            {
                File.WriteAllText("C:\test.txt", "test");
                WriteAllText("C:\test.txt", "test");
            }
        }
    }
}

I don’t think I liked this new feature. If you see a direct method call it feels like it’s a member of that method. But now it’s possible that method can be defined inside a static class somewhere else. I think it would just cause confusion and doesn’t add any benefit.