i agree with tightslot and yvonne lynch almost everyone will know at the time of booking the airlines seat pitch so if you go cattle class dont be bitchin when a seat goes back!! you get what you pay for .
Seat pitch is not the only determiner of useful/comfortable space. It also involves seatback thickness, angle of rake/recline of the seat back, seat base height and position of the pivot to name but four.
For example, KLM has two types of seating in its 737-300s, the new and the old. While both are tight (same pitch), the new seating has thinner, more rounded backs and a higher seat base. This means the new seating is just about tolerable, while the old is painful even when not reclined.
Similarly, on the rails, I can sit comfortably in a Virgin Voyager seat, but not in an old Mk3 seat on an IC125, despite the latter having a *far* more generous actual pitch.