The program on the search for dark matter/ energy was fascinating. It also pointed up how little we actually know.
That is one of the things that I have enjoyed the most about my career at NASA--although the programs that I have been privileged to work on have increased mankind's knowledge exponentially, the primary thing they have proven is that our lack of knowledge is truly profound. The more we learn, the more questions are raised!
The very concept of dark energy is so counter intuitive to me that I really do doubt its existence, but the questions raised by our observations have to be answered. It should prove a fascinating future for science!