I do agree with the guy below about how this is probably mostly evaluated by fondness of these characters. But the quality really is good, and the fact that they remain voiceless is definitely in good taste.
Smooth animation made this a pleasant, albeit short, piece to watch. However I feel like this was a rather dull strip to animate, lacking any of the humour, imagination, or poignant moments that made Calvin and Hobbes the comic strip that so many love.
Granted, this might simply be a tribute to the strip. Fine, but all I'm say is that if that boy had been a random little boy who had been tackled by a random animal, I guarantee that people would be evaluating this short based on its own merits instead of just being giddy over seeing Calvin and Hobbes animated.
Hey look, a video on NG that isn't a bad parody of something, bravo!
Four stars all around. And I agree that we shouldn't give Calvin a voice, or anyone else from the strip for that matter. It's the very same reason that Waterson never signed a single merchandising contract for his strip. I think what you did here was a tribute and an excellent one to one of the few (only?) comic strip characters to ever have a soul, thanks to the care and nurturing of his creator. Also there are many Calvin and Hobbes strips that have little or no dialogue to begin with so you've got some fertile ground here. Keep it up.