Hi
I did this as my first JY trip in July this year. I had a fantastic time and met some great people. I am actually going to Paris in November with a couple of friends I met on this trip!
I'm 33 and although one of the youngest (there were a couple of guys slightly younger than me), age really wasn't an issue.
The tour itself is pretty packed but you do get to see & do some amazing things. As our fabulous tour guide said - you can sleep at home!
Have fun if you go!