The world editor has its strong points and its weak points. Coming from a radiant environment, it feels a little clunky until you get used to it... but the true real time display in the perspective portal is really nice. Being able to see the scene graph is pretty cool too once you understand what you are looking at.
It is probably easier to build the actual geometry in another application like MAX or Maya or whatever your personal 3d authoring preference is and then import in COLLADA format. It doesn't have to be done this way though.