Currently GE does allow users to walk around however this is limited to its existing ground plane. If any imported content / 3D model sits above this, there is no collision detection thus users will just fall through the mesh.
Users can zoom down to eye level however navigation from here can be tricky and cause confusing results.
SketchUp provides a great walk around tool. Currently, this is a beneficial alternative and due to both GE and SketchUp being owned by Google this is surely only a matter of time before it is implemented.
Posted by cwayling 