I just flew SFO-DUB on Aer Lingus and it was a delightful flight. It's a day flight which makes it easy to move about the cabin since you aren't interupting anyone's sleep. Although you will be tired when you arrive the next day. Their seats are comfortable. You are feed two nice meals and a large snack plus all the beverages you want. Movies run on a loop, with the seat backs holding the screen or you can play games on them.
I did find it interesting that the only ones moving about the cabin were the Americans. There is also a nice place to stand, out of the way, in the aisles by the center cabin bathrooms.
I have no idea how easy it is or the price to get from Dublin to Nice.