I have tried out ShiVa and apparently it has a very feature-rich and stable editor.
It has an interface similar to Blender to some extent. E.g. you are able to change the window types - and there are lots of avaible window types you can choose from:
Scene Editor (WYSIWYG Editor and game preview), Web Navigator, Script Editor, Data Explorer, AIModel Viewer, Particle Editor, Navigation Mesh Editor, HUD Editor, Material Editor and so on.

In the Particle Editor you can adjust your particle effects by setting the bitmap, max. number of displayed particles, life time, speed, gravity, friction, color change (up to four colors) a.s.o.
You can see the results in the Scene Editor immediately.

In the material Editor you can (surprise!) adjust the materials of your entities. You can load the material of an object by just clicking on the object with the material picker. Then you can customize dynamic and static lighting methods (per vertex, per pixel or toon shading), shadowing, texturing (e.g. normal mapping textures for shaders), colors and general stuff.

In the Attributes Editor you can even decide if your selected entity should be reflected or refracted (water or refraction shaders) and you can set its activation distance and fade-out distance.

Of course you can move, rotate and scale objects in the Scene Editor, change the display mode (textured, wire frame or gouraud shading) and so on.
However I havent managed to move the camera around yet ... I have pressed every single key on my keyboard, but the camera doesn't want to move. This is a pity, because it is not really possible to edit a scene with an immobile camera.
And don't dare to recalculate the lightmaps of a scene, as it can be very time-consuming. Recalculating the lightmaps of the small car demo in a slightly higher resolution took about a half hour to complete.

BTW: To get the car demo (or other demos) started, fire up ShiVa, click into the Web Navigator and look for the car demo link. There you'll find an instruction (in english) of how to start demos.