Gabriel:

Yes, row 12 on the AC A340 is the best. Row 31 has about 2" more space than 12, but there are some negatives that make 31 not as good:
-The FA sits right in front of you during take-off, landing.
-There is a full size door at row 31, and this eats into the space avail. to the person on the window. This may cause that person to "spill" over into part of the leg sapce of the asile passenger.
-The washroom is right in front of you (two of them!). On a long flight, the constant "going to the lav" by others may be unwanted.
-row 12 has a small screen for video right in front of you, as well as the large one in the centre. In row 31, there is only the centre screen, and the viewing angle is quite hard on the neck.

I did 12A YUL-LHR last October and had quite a good flight. There is, I would say, 39-40" of space in row 12. I find the window to be best - you can lean up against the side of the aircraft.

Hope this helps.

[This message has been edited by Fisch (edited 09-08-1999).]