The way that the animals live under Napoleon is essentially no different than the way they lived under Jones. There is only one real difference that I see -- no animals are killed for food under Napoleon (although Boxer is killed for money, but at least it is after he is already pretty close to death).
Under Napoleon, the animals have little choice in what happens to them. They have to do what Napoleon says or they will die. The same was true under Jones. To me, this means that little has changed.
Napoleon is similar to Jones because he is using the animals' work to make a comfortable life for himself. He cares mainly about himself (and the pigs) and does not care if he is being fair to the other animals.
The previous post is essentially correct that little changes on the farm except for the fact that the animals are not killed and eaten. However, animals are killed--not for food, but for political purposes and, in Boxer's case, for money. However, the animals (the non-pigs, anyway) eventually work harder and longer hours during Napoleon's rule than under Mr. Jones. Their rations also eventually diminished to a smaller amount than when they were fed by Jones (or at least when he remembered to feed them). Of course, the animals were told differently by the pigs, so they weren't really sure if they were getting less food or not; they do know they were hungry, however.