I saw this opening day, and am itching to see it again soon!
I LOVED this, thought it was brilliantly funny, heartwarming, and the best of the series. I personally feel the Ice Age movies get better and better with each one, and am saddened that this one hasn't been getting any of the attention and buzz it deserves (I don't know about you, but I barely saw any trailers for this on tv before it was released...and they've shown even less trailers for it since it's release last week).
Buck was a fantastic new addition to the cast (unlike Crash and Eddie, who were okay in the 2nd movie but more annoying and unlikable a good portion of the time in the 3rd), the animation was stunning, and I was laughing pretty hard throughout the entire film.
Diego didn't really do much in this movie (his problem was introduced and then kind of brushed aside), but that didn't really bother me since he got more focus in the first two films. Sid got more attention in this movie, which I was thrilled to see because he's my favorite.
The rumored 4th movie's plot sounds interesting, and if it does happen I will be seeing it for sure, but it also has the potential of being not-so-good. I'm hoping that it will be even better than the first 3 (since that's how these movies are for me), but I'm also hoping it will be the last one (since I have no idea how they'd follow up to the 4th if the plot will be what it's rumored to be). If we don't get the rumored 4th movie after all, then I'm okay with that too because I felt this 3rd movie was a nice place to end the series as well.
I am so happy that this movie didn't end up being a huge and unfunny disappointment like Shrek 3 was (which has two sequels and a spin-off still on the way, unless they've been scrapped since the announcment right before Shrek 3 came out).