Don't watch a CGI (digimation or whatver you want to call it) film thinking it's going to be as good as a classic Pixar, it's not. Not even the recent Pixars are as good.
IA: TMD has only a vague narrative (Mark Kermode described it as "the death of narrative cinema"), but at the end of the day, it's some pre-historic animals making their way down a valley to escape an impending flood. That's it, does it need anything else? No. It's got some basic character development for some of the main protagonists and some actually quite dark moments and some comic genius at times.
What it's not is Toy Story, what Ice Age: The Meltdown is, is a heartwarming and very entertaining flick.
"I think I coughed up my spleen"
Ice Age: The Meltdown - 7/10
(Next up The Da Vinci Code, cheers mum's Sky Movies premier, cos that means I don't have to pay for it.)