Welcome to the forums!
Yes, I got to try Artifex Terra when I was doing Ogre3D some time ago, and it really is a great terrain editor!
Here's my built and a little test video 2 years ago
I am currently in the process of reworking it and making it more agnostic and open, as in integrating assimp and plugins - specially export / import geared towards various engine formats.
I just thought it was more focused on Ogre3D so I did not include it on this list but it's good to hear if you do have plans of making it agnostic/open and Urho friendly.