We were last in Nidri about 3/4 years ago. At the time it was quite noisy if you were staying on the main street, mainly because of the mopeds that used to go up and down all night long.
They were building a bypass at the time, so it has probably improved the situation.
Nidri is ideal if you like boats as there are a couple of good day trips to other islands and ,also, you can take your own boat out for the day and visit deserted beaches, have a good look at Skorpios and go to Meganissi which is on the other side of the water.