The exhibits were pretty cool, but each took literally 15-30 minutes to go through. They seemed as though they changed quite often, so Im sure it would be better if you actually lived in the area and went back every few months. The cafe is also amazing!
We actually went during the May 18th ceremony, and were able to watch a video, hear a presentation (in korean), and listen to people sing. Just happened by chance.
The area that this museum is in is what made the day for us. The walk around is gorgeous. Not only that but the Gwangju Folk Museum and the Gwangju National Museums is so close that you might as well do all three in one day.
Keep in mind that Monday all of these places are closed! Best days to go are Tuesday to Friday.