I just wanted to write and let you know that I visited Vaux today. It was a mixed experience.
The chateau itself is still private and very well preserved. Much more so than Versailles and almost reminiscent (in condition) to some palaces I have seen in Germany. Having said that the fact that it is private can also make this a somewhat expensive visit. Particularly for families.
The shutte stops running for several hours in the middle of the day. To avoid that time period I left Paris (with enough cushion room to allow for delays) and headed out to Vaux (located in Melun). Their website specified that it takes 30min. to get there from Chatelet-Les Halles via RER-D. Not so . . . or at least not always so!!

Imagine my surprise when it took an hour and a half to get to Melun!!! Of course by that point I had fallen into the no shuttle time zone. Since I was by myself I had the pleasure of paying every penny of my 15Euro taxi ride.
I am under 26 so the entrance to the chateau was discounted for me. I paid 13.50 for the entrance to the place, access to the dome (2Euros extra), and an audioguide (1.50Euros). The Chateau also prohibits picnics so you have no choice but to eat at their restaurant. Certainly a bit of a rip-off if you don't want steak or ice cream. In fact, some French people at the next table kept on joking that since they had tasted their significant other's food they would probalby be charged a euro on the way out!
On the way out I took the shuttle which only cost 3Euros. That was good - even if I had to stand.
Oh and on the train back I caught a regular SNCF train back to the Gare de Lyon and I got there in about 10 minutes or something. It was lightning quick and a welcome change from my morning ride.
All in all the place was absolutely beautiful and historically very significant. I enjoyed my visit at Vaux and I would do it all over again. Having said that I was a bit surprise to discover that this day trip cost me over 50Euros.
Anywayz, still very highly recommended! Although as an aside I would also suggest visiting the Chateau de Chantilly. The place itself is not as well preserved but their art collections are simply magnificent! That and the library there (an extra tour) reminds me of the one in "Beauty and the Beast." Be still my geeky heart!