Experimental Economics: Hard Science or Wasteful Tinkering

I take it that in raising the question "What have we learned from experimental economics" under the broader umbrella of "controversy" the point is not to solicit a catalogue of experimental findings, but rather to signal the more pointed question: are we learning anything at all, or at least much that is very useful form experimentation in economics. As a practising experimentalist, I am convinced that experiments do have the potential to make a significant contribution to knowledge in economics.