I always put my seat back, but I try to do so in a pleasant and courteous manner. (read: slowly)
I figure, if whomever is behind me really doesn't want my seat back, they can pickup a pair of
Knee Defenders for 15 bucks and I'll be thwarted in my evil plan to destroy peoples knees.
I'll also fully endorse the stool options as proposed by
BNA_flyer with a slight exception: If you whine about your stool, the FA gets to take the seat-top off and you must spend the remainder of your flight sitting on the pole.
-SF