The ending of Animal Farm is brilliant. It shows clearly that nothing has really changed. In fact things on the farm have gotten worse. We see this in what Mr. Pilkington says to the Napoleon. Here is what the text says:
Mr. Pilkington once again congratulated the pigs on the low rations, the long working hours, and the general absence of pampering which he had observed on Animal Farm.
The animals are working harder, getting less, and there is no real change in leadership or the use of power. The reader knows this all along. However, in the end, when the pigs turn into men and Clover’s eyes cannot tell the difference between Pilkington and the other pigs, the reader is surprised at what he knew all along. Orwell has brought home the point in the most explicit way possible.
In light of this, my reaction was one of sheer delight. Power corrupts absolutely, and Orwell shows it through a transformation.