I spent nine nights at the Adina Hackescher Markt a year ago and nothing seemed worn to me. The room was large, with a mini-refrigerator, dishwasher and, I think, a microwave. For me, the location was ideal, with the S-Bahn a block away, the U-Bahn a couple of blocks the other way, a bakery and grocery around the corner, a lot of restaurants within a couple of blocks, and Museum Island about a 10-minute walk. I thought the hotel breakfast was overpriced, but the bakery was fine and several restaurants also had full breakfasts.
Checkpoint Charlie itself is worth a quick look, and there are some museums nearby focused on the Cold War. I'm sure it would be fine, and the hotel might be better, but I think the Hackescher Markt area is more interesting and convenient.
EDIT: The Melia where Continental stayed sounds very good also. Probably a denser neighborhood but hard to beat the transportation connections.