These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Art: Possibly one of the most beautiful looking CG animated films ever made.
Best Known for the Fanservice: An animated GIF of the beach ball bouncing off a lady's badonkadonk can be found around the net and for a lot of people it's the most memorable part of the movie.
Though this wound up as something of a detraction when it became the focus of one of the trailers, as many movie-goers dismissed it as the kind of "crude humor" type film Dreamworks was known to release in the mid-2000's (although Rio is done by Blue Sky Studios) and not the more adventurous film filled with Awesome Music that it turned out to be.
Big Lipped Alligator Moment: Nigel's Villain Song. It comes right out of nowhere, adds absolutely nothing to the story, and is never brought up again. It at least gives some Backstory for him and explains why he's evil, but this aspect is never brought up again either, probably to keep the auidience from having any sympathy for the guy when he's clearly meant to be pure evil.
Crowning Moment Of Awesome: Linda, driving like a maniac behind the wheel of a massive parade float, crashes through a chain link fence onto an airport runway and plays chicken with the smuggler's twin-engine plane in a desperate attempt to stop them taking off with Blu. It almost works too.
And moments later, Blu has several in a row when he busts out of his cage, frees all the other captive birds, and takes out Nigel — and by accident, the plane itself — with a fire extinguisher and a bungee cord, then saves himself and Blue from certain death by flying for the first time in his life.
Crowning Music of Awesome: DJ Dero's Batucada in the trailer is only the beginning (and is heavily sampled in the soundtrack). The first two minutes of the movie are set to a Brazilian samba.
Nearly EVERY one of the songs in the movie is this.
Jewel's solo in "Hot Wings I Wanna Party" is one of the most beautiful parts of the entire movie.
And a great contrast. Blu's a natural talent at the rapid motions of street-style samba; Jewel's flowing motions evoke a much more formal, classic style of samba.
John Powell's score is a bit overshadowed by the songs and isn't exactly How to Train Your Dragon but it gets some moments to shine, particularly "Flying" towards the end.
And now the sequel has Bruno Mars featured in it! And he really gets his chance to shine with his introduction song, "Welcome Back", a sweet sounding serenade dedicated to Jewel's return to the Amazon.
Die for Our Ship: Poor Roberto's already getting this from Jewel/Blu fans, and the sequel's not even out yet! They're also clearly ignoring the fact that Roberto is repeatedly described by official sources as being a genuinely good guy who just happens to be a bit of a show off, and while Word of God confirms that he's still carrying the torch for Jewel, no evidence has been seen to imply that he's actively trying to undermine Blu and Jewel's relationship. That being said, again, the movie's not out yet, so the fan's outcry may turn out to be justified when it does, especially considering the fact that Roberto has "a secret" of some kind.
The Scrappy: Roberto is already getting this from fans, even if; or because, he's voiced by Bruno Mars.
Sequelitis - The sequel is not as well received as the first.
Squick: Any scene where Luiz the bulldog drools on the main characters. Although he has stated it was a medical condition.
Unfortunate Implications: A plot in the sequel is apparently Blue competing over Jewel's affection with a new guy, even though they already ended up together, and with children. It remains to be seen if it's the actual dilemma of the movie however.
Given the way her father is depicted, it's possible that he's trying to set her up with a "better man".
Wordof God states that it's mostly paranoia on Blu's part.