I have just released a demo version of my terrain editor for people who are interested. It is a full fledge outdoor terrain and world editor where you can edit terrain, paint textures directly onto it, import mesh files, add skyboxes, fog, lighting, ect.....
You can read the full description of features and capabilities on my web site
If you download the demo, please feel free to leave any feedback or bugs in the forums so that they can be worked out before I release the final full version. Thanks