The biggest mistake we made in Berlin was going to the Checkpoint Charley Museum.
It is an incoherent grab bag (what does Raoul Wallenberg have to do with the division of Berlin?) dominated mainly by the history of the Berlin Wall. There are relatively few artifacts here and lots of writing on the walls. I could make out no chronological progression as one moved from one small room to the next.
I would recommend that nobody go here, but if you are claustrophobic make a special effort to stay away. There appears to be no crowd control--as long as you are willing to plunk down the outrageous price of 12.5 Euros they'll shove you in on top of the milling mob already trapped there.