Frank, it's not very obvious to a software engineer like me what's so special about the editor. To me it seems only the megatexturing and this sprite/stamp management.
But all in all the editor looks quite cool xD
Yes. This is true. But exactly these 2 features are amazing for many arists around the world. You have totally freedom to paint whatever you want at the terrain, not only 3 or 4 textures. You can add individual skid marks, swards, pebble or any traces of destruction. You can approximate reality even more.
They just threw some more constraints away to allow another degree of freedom.
And to tell it with simple words: It is like a paint program but in 3d.