Get rid of camera control widgets and use mouse and keyboard to pan, zoom, rotate, etc.

Add manipulation widgets (rotate, translate, scale) with the ability to select multiple actors at once.

Improve skinning, rigging and animation support.

Add C++ API (to Poser). Some plug-ins may require the performance and integration that current Python API simply doesn't offer. That would help to address my points above by the way and points raised by other posters in this thread.