The excitement about getting for free because I was a DB employee was destroyed when I arrived on Monday and found out admission is free on Mondays for any schmo off the street. I had been so careful to make sure I brought my employee ID along but they didn't even bother looking at me as I walked in, giving me a silly but deep sense of disappointment. There is definitely something to idea of exclusiveness that makes everything a little shinier and I am embarrassed to admit that I am not "above all that stuff" like I thought I was...
Despite this, the exhibit was fantastic and I really liked the sculptures. The exhibit has now changed to the 2012 Artist Roman Ondak, and although I haven't seen it, I definitely recommend stopping by the one-room exhibit hall if you're in Berlin (preferably on a Monday!). It's in a central location and you wouldn't need more than 20 minutes to see everything - easy to fit into any schedule.
A funny side story, DB did a competition where two employees would be picked to have their faces cast for this exhibit. I have no idea who won, nor which sculptures they ultimately became a part of, so I spent a significant amount of time walking around the room (and later my building) looking at the faces to see if any of them seemed familiar.