We flew with Easyjet a few weeks ago and they have fixed seats too. On short haul I don't, but long haul - yes although it's only when the lights go out and there's no food.
What I hate more than the reclining seat issue is sitting in front of children when they're allowed to kick my seat! OR sitting in front of them when they're allowed to peer over the back of their seat and dribble onto me!! Rant over!