As long as you're seen to be making an effort to keep child calm and entertained then I can't see why anyone has the right to complain in any cabin. Long haul i've only flown in Y and Y+ with my 7 year old, the first time i flew long haul with her when she was 6 months sitting middle 4, the two people in the middle complained endlessly about the bassinet (they'd specifically asked to move after walking past and seeing the two empty seats when we were already seated) but the person on the other aisle came round, sympathised saying they normally flew with two kids and would i like them to entertain my daughter so i eat/use the toilet etc, made me realise that flying with kids wouldn't always be bad and that there are nice people out there well occasionally