reduced sensitivity won't be an issue, from the performance of touch-screens I've seen in (roughly) similar installations. But computer periperhals are known vectors of communicable diseases (you've seen my rant in other threads ) Touch screens can get grungy, especially if used while in the proximity of food being consumed. MY bet is cleaners won't be sanitizing (hah!) them, either.
I think I'd find the seat-bashing about all I could take. This sort of thing sends me screaming into biz or first, where seatback screens don't exist as such.