I really like this design a lot, and I don't really say that a lot for White Tees! The pastel colours look excellent and make it look retro and clean at the same time!
I don't know why, but the design on the fifth person (sledding down backwards) looks a little off. It honestly looks like he is sledding up the hill. Also, the shadow of the person about to smack the groundhog in the head seems to contradict the shadow on the groundhog himself.
Also, have you thought about placing the one person climbing the hill to go back down on the back of the shirt.
I really like this one - no joke - I'm just not sure you would see the ground hog at a glance - could you emphasize it somehow? - check mine out http://threadless.com/critique/404204/Paper_beats_scissors I need critics