I used the JJ3 U1 editor to create an experimental level for jj3 to show off what can be done in the editor (limited to my skills of course) and it turned out to be quite a fun level to play. It has some minior terrain (which is hardest thing to do), but most of it is an inside environment. The level was available for download on Nimrod's forums for a while, but no longer after the format of my server. I think I still have it somewhere.
Unreal editor is one of the easiest 3D editors to use I've seen and it gets better in every new version.