I saw it today with my three- and five-year-old kids. It really was good, maybe a little more emotionally-engaging than the previous movies. From an adult perspective, it was very much a story about relationships. While it still maintained the broad friendship and trust themes from the previous movies, it also delved heavily into such areas as neglect and loss.
Parts were very poignant, including the end. I didn't expect to see a scene where the toys share a last moment together, accepting that they're about to die.
Oh, and the kids liked it too.