Deceleration after landing (or during an RTO) is usually much greater than acceleration during take-off, so more comfortable to be facing backwards for landing than forwards. Once airborne it doesn't really make a difference, I'm not sure anyone would be able to tell which way they were travelling.
Airplanes normally fly nose up (takeoff, cruise and for periods during descent and approach) and flat during rollout. With rear-facing seats, won't you spend most of the flight relying on your seatbelt and the curvature of the seat cushion not to slide out of the seat?
Acceleration may be less during takeoff than during landing, but some aircraft pitch up to some very uncomfortable angles during initial climb.