score:3
Unfortunately, my flight was very late, so I didn't actually arrive at Nice airport until just before 1am. The first thing to note is that the N100 nightbus is very prompt about leaving, and at 30 seconds past 1am you'll see its rear lights disappearing off into the distance...
The bus stop for the N4 nightbus is not well signposted from the airport, and the route is a bit complicated by various carparks and roads that don't seem to show properly on maps. Don't expect to be able to find it very quickly your first time trying! However, it is more frequent than the N100, so may work better.
Generally though, the bus service is pretty good in the day and early evening, and not too bad in the late evening, it's just around midnight when things start to get hard, and you'll probably need a delayed late flight (like mine...) before you'll end up with issues.
At 1am, there was a huge line of taxis available at the airport ready to whisk people into town. When I returned at 1:20 (having given up trying to find the N4 bus stop in the dark), there was a short wait for a taxi to arrive. At that time of night, taxis are a flat rate of €35 to the centre of Nice. I believe there are different flat rate prices for other areas. (uncovery's answer has a link to a slightly outdated price list)
Oh, and one thing to note for coming back from Nice to the airport - at the moment (2013) there's lots of work going on around the station, and Place Massena. Lots of bus stops have been temporarily moved, but there are maps around which show the new locations. The #99 bus (airport <-> station) and #98 bus (airport <-> city by coast, runs later) are both very good and worth getting, but allow a bit of extra time to find the stops!
Upvote:4
In general, you can always take a taxi. Taxis are around at the airport as long as airplanes are operating. There is a page in english made by the airport regarding the taxi transfer and the night fares. You can also call a taxi company like this here to pick you up in case there is none at the airport by chance. If you want to go 100% sure that you will get a reserved pickup, you can book a kind of limo/taxi-transfer on pages like this here.
However, there are also options by night bus ("Noctambus"). The issue here is that the city night buses do not stop at the airport and the regional ones do not go to the train station. Also, the Noctambus is for people leaving the city, so it gets more complicated going to the trainstation downtown. I will describe it here for completeness but as you will see this is quite complicated and a taxi will be much easier. So there are 2 ways to do this via bus:
This is the map for the all night buses. On the bottom left of the map you have the airport. You can see that the yellow line (N4) stops in the east (Gare SNCF St. Augustin) and in the north (March Gare). According to the N4 schedule, this would be at 0:50 and 0:57 respectively. This one will bring you downtown, but it does not stop at the Gare Nice ville either, since all night buses does so only on the way leaving the city, not when they come back. You will have to walk or find a taxi instead once you are downtown.
If you take the regional bus, (The grey N100 line on the map), you can board it at 1:00 at Terminal 1, and get off at Gambetta-Promenade or Le Port and walk from there or take a taxi if you get one.