The con location is easily reachable by public transport from both Berlin airports.
*snort*
Erm... yeah. We'll have updated travel information on the web site sometime in January, I swear. 
*chuckle* The TXL bus is an experience

And then so much S42 you could easily be in another city by the end of the trip, but it's still Berlin. (Well, it's a huge city...)
Tony: definitely stay a few days before or after the con and have a look around in town. You will most definitely not have the time during the con to do so, but Berlin is worth to see at least once. As said, it's big, and it has a great history. The Wall is definitely a must-see: both the remaining parts around the East Side Gallery, and the memorials near the Nordbahnhof. I personally enjoyed the Oberbaumbrücke in the evening, and going around with the U1 is also nice (it's a high rise rail for many parts of its journey).
My experience with cons seems to be that if you stay after the con and get yourself busy being a tourist, it's much easier to fight off PCD
