The two aspects of this movie that I don't think are covered by the review are a) Ariel's relationship with her father, and b) the violent end to the Sea Witch.
My 4 y.o. son is always a bit upset with how King Triton treats his daughter, esp when he comes into her little treasure room and destroys all her "human stuff." So it's definitely something that leads to discussions about listening to each other, being patient, not losing your temper, etc.
Also, Ursula the sea witch is killed at the end in a pretty gruesome way; she turns into a giant monster, and Eric the Prince steers a boat toward her abdomen and impales her with a sharp jagged piece of wood on the boat.
And at the very end, Sebastian the crab hits the French chef with a large wooden beam, knocking out all his teeth.
But, if you go in prepared for those scenes and how to address them, they aren't a terrible problem. Ariel's sweetness, the wonderful songs, and the entertaining storyline make this an excellent kids movie.