If you're going with an architecture student, you'll want to definitely check out Potsdamer Platz. All sorts of new buildings going up, and even from one year to the next, I would say you'll see a whole lot of change.

For a different museum, try the Hamburger Bahnhof, (U Bahn stop Zinnowitzer Str. or S Bahn, Lehrter Bahnhof)
http://www.hamburgerbahnhof.de/

Hotels: I'll second the Westin as one of the best hotels in the city. Be sure to leave time for a sauna/soak in the hot tub!