Hiya -
I had the opposite problem - on a night flight, I reclined my seat - after the food trays and drinks etc were done with - they dimmed the lights, and warning the lady behind. I wanted to sleep - it was 2am US time.
As soon as I reclined she thumped the back of my seat really hard and said "NOT THAT FAR - I'm watching the film". Well, I'm sorry, but I wanted some sleep, so stayed reclined - I know it is hard when the screen is that close - but a) it was NIGHTIME and b) she could recline too...
On a day flight, I will recline slightly - after the meal, drinks etc, just for comfort - the seats are not great after a couple of hours, but would not recline fully... though I know sometimes people are not on the first leg of their flight, so do understand if someone in front of me needs to recline and sleep. But as the OP said, it is nice to get a warning.
I wouldn't let it spoil my flight though - if you have to grab the seat to get up, well that's what you have to do - and the person who is reclined must be prepared for that...
There's a lot worse than someone reclined in front of you! Someone behind me put their stinky, smelly foot on the aisle arm-rest next to my head once bleugh!!!

And couldn't understand why I asked them to remove it!!!!!!! Then there's kids behind who kick your seat in time to the music... kids in front who hang over the seat watching your every move.... rowing adults....whining children.... smelly bottomed babies being NAPPY CHANGED right next to you.... teething babies.... I could go on..... please stop me.....
The most annoying was the child behind who had a fascination for dropping and reclipping the tray - his mother eventually offered to swap seats with me - after 45 minutes!!!
Hey ho, they wonder why people find flying stressful! I'm sure it has nothing to do with fear of crashing, just other people.....
Tessa