Funny, when I went SIN - LHR earlier this year I specifically chose the flights with SQ's 777 over the 380. The main reason being LHR T3 cannot handle the bags coming off a 380(!)
I didn't notice any issues with it, my cattle class seat was fine, as far as cattle class can be and I think I had enough air. It was a bit lumpy at times but I didn't notice anything out of ordinary.
I do agree that the 380 is very quiet, indeed the quietest plane I have ever been on and at times when I have half woken up and not heard any engine sounds it is a bit unsettling...