I agree that most complaints of Noise at the Poly are overblown. I've stayed both Lake View rooms and standard view rooms at Poly...all without issue.
If you're a lake-view room, yes you'll hear the boat horns. Typically they run from the early morning to the late night. I can totally understand that if you're a light sleeper, they might keep you awake. I am neither a heavy nor light sleeper and I was perfectly fine. Never had a problem falling asleep, nor did they wake me up in the morning.
Same goes for noise between the walls and in the hallways. Nothing out-of-the-ordinary for any hotel. Poly DVC is neither more nor less noisy than any other hotel. If a child is having a tantrum, screaming, etc...then yeah, you'll hear them.
My recommendation is to bring a white-noise machine or find a white-noise app for your phone. Crank that sucker up and have it drown away anything that might keep you up.