We are trying to CAD then build... many of our parts this year were CAM driven, so the model is a requirement. We did do a fair number of 'virtual prototypes' to shortcut the time required for physical ones. Like this one where we tried to optimize our arm lengths. I think the upload to You Tube took longer than the entire analysis.
http://www.youtube.com/watch?v=1xIODUn0EbI