Well, Berlin is a wonderful city but it's airports are lousy. They are very old and overstretched.
Tegel was built for about 11 million passengers/year. Today there are more than 20 million passengers/year.
I already thought it is better to fly to Hamburg or Leipzig and take the ICE to Berlin rather than the Tegel Express.
Nevertheless I arrived at my destination on time and experienced a breathtaking sunset approach!