It wasn't just AICN that posted a negative one, Variety and Hollywood Reporter gave it bad reviews as well. No doubt if the reviews were good, the embargo would not have happened. Its very rare that a studio enforces this--especially when critics had been INVITED to the early screening.
Sunday--you make a good point about live-action vs animation for the humor. I think the main thing is that this is a film obviously designed for ten year olds--bad slapstick and kiddie humor is part of the genre. As far as box office, I doubt this will crack the $50 million mark; it'll do $35 million opening weekend, and then really quickly taper off to at least half of that in week two and by week four it'll be gone from the weekly top 10. This movie won't get the repeat business from Star Wars fans, aside from opening weekend it'll be 90% kids. It doesn't really matter though--I estimate the budget for this film at about $10 million. It'll be the most profitable film of the summer.