Make that "good hearing or good headphones".
Actually, make that "good hearing or low impedance headphones".

I tried listening to the N810 with old Ultimate Ears SuperFi 3 studio earphones, which only have 13 ohms impedance. It was impossible to use them without the included airplane adapter. The noise was very noticeable even at moderate volumes - felt a bit like listening to a walkie-talkie.

I have high hopes for the N900 because of the included (if we can trust the kernel sources) TPA6130A2 headphone amplifier. On the N810, volume control was purely on the digital side, causing much worse SNR with decreasing volume.

I'd love to see specs or reports about "ears-on" experience, too.