I always have on hand an American>Euro and American/UK plug adapter, but while living in Europe until recently I found it easier to travel with a European Nokia charger for my N800. Unless you're traveling with other electrical items it might make more sense. I will be easy to find in any electronics or mobile phone store and should not cost more than $20 US.

Berlin is a fabulous city, and one of the great bargains in Europe. With the recent decline of the Euro I think you'll find lodging and dining prices similar to the US, depending on your tastes.

As discussed by others, the beer, especially pilsners, are excellent. Of particular note is the traditional Berliner Weisse. It's tart/sour and tough on the uninitiated palate. Even many Berliners add syrup or raspberry juice to tame it. Enjoy it with a Thüringer Rostbratwurst.