I've flown on UA's 777's (many of them), A CX 773 and been on the #1 777(though not in cruise) and I find the 777 to be as quiet as the A330/A340 and I don't find any of the dryness problems described. I do agree the initial climb buzz of the PW4090's/4098's can be quite loud, as with the A320 IAE engines, but in cruise I find the aircraft fine, very smooth and quiet and I can sleep quite well on them. They don't seem to have the gentle throbbing vibration that goes through the cabin that I've felt with the 744 (UA) in cruise which gets very noticable during a 13 hour transpac flight.
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RichardMEL, UA 1K
A Star Alliance Member.