I stayed six nights at The Westin Grand in Berlin. The location is simply perfect because it's right between the Brandenburger Tor, Museum Island and Checkpoint Charlie. As soon as you step out you've got the Galeries Lafayette, a metro station, and lots of other high end shops.
I would completely recommend this hotel and stay there again. The only negative was the price of the Internet connection. 15 EUR (USD 21) per day (!) was a little bit over the top... but I paid for it as I didn't have any other choice.
The Westin Grand