The 737-400 offers an average pitch of about 31 inches (Seatmaps.Net was unable to obtain exact data). Seats on the starboard side (D, E, F) have approximately one additional inch of legroom for some reason. There is an audio entertainment system. You can purchase headphones or bring your own, but you will need a Y plug (the kind that has two 3.5mm pins on them. Lufthansa uses these on many aircraft as well). Adapters can be used. Also, there are video monitors above the aisle. The first monitor is stowed away for takeoff and landing, so if you'd like to see the airshow map and flight data during this time, don't pick the first couple of rows. A warning: On many Air Berlin flights smoking is permitted in the rear section. Due to the air circulation on board, smoke may be a problem behind row 9 or so.
While this row offers additional room for your knees, it is a little cramped in the foot area. It seems that if you take off your shows, you can put your feet up against the wall without being yelled at by the crew. The big advantage of course is the fact that nobody can recline into you. You might have a little trouble seeing the viedo monitor, since the angle is a somewhat unfortunate.
Acceptable Economy seats with a pitch of about 31 inches on the left and 32 inches on the right side.
These seats in the smoking section have limited recline.
Some passengers report that this seat is occasionally called 12A. Also, on some aircraft apparently both A and B exist, making it a regular 3-seat row. If you do ge a two-seater, the left seat provides you with some extra space. Of course you cannot lean against the wall there.