My first post here
About Tegel/Schönefeld/Tempelhof: The new Brandenburg Airport is being built on the site of Schönefeld. When you fly over it, it indeed looks huge, but be aware that at the moment it's about 2 airports
The north is the old airport (of which one runway will be used for the new one), the south is the new. http://en.wikipedia.org/wiki/File:Map_B ... ed_BBI.png
shows pretty clear what is new/old.
Regarding Tegel: it's a pretty different layout, with a tiny distance between the entrance door and the airplane. Yep, it's old and yep it's about time they replace it. Last time I've been there was in May and I sat outside the terminal building for what seemed to be the last time I could use Tegel. I love that airport. Connection to the city is horrible (I personally dislike buses - no metro available), it's cramped and old, but it still has that really nice feeling of how flying used to be: get out of your car, walk 15 yards and get in your plane. No huge shopping malls, just planes.
Tegel and Tempelhof were the airports for West-Berlin, Schönefeld for the East. Tempelhof closed in 2008, I went there one week after the closure. Weirdest experience I've ever had at an airport: closed, still some luggage carts outside, but still 100% an airport.
The Brandenburg Airport should have been opened a couple of months ago, but a couple of WEEKS before opening they found out it wasn't ready... Opening is delayed until March 2013, if I'm correct.