It won't be a ghost town, but it's a bigger holiday than christmas so a lot of people spend the time with families. If you're there for NYE itself it's great, they do a firework display from Place Concorde and you can be guaranteed it won't be an early night! Very very busy night in the city.
I think Musay d'Orsay closes for a few days around that time, but the other big ones are open. Check websites for anything special you want to do maybe.
Book well ahead (maybe even phoning ahead now) if you want to eat out on NYE also. A place I always wanted to try was the roof restaurant of the Tour Montparnasse - around 50 floors up, would be a lovely place to eat and see the fireworks at midnight.
Enjoy it!!