Yeah, what Peter said...
Though I should emphasize that I don’t have any post-secondary training in biology and it really bugged me that all the Pandora critters seemed to have six limbs, and the Na’vi only had four, while everything else seemed pretty well thought out. (Though it did seem there were way more predator species than there should be, but let’s face it, the predators are more fun for the story.)
The cat chick was smokin’ though, and I’m not sure if it would have been as believable if, as Peter suggests, Neytiri had been a four-armed, two legged banana slug and the human fell for her. (Unless it was Captain Kirk driving the Na’vi avatar, in which case, obviously.)
Clearly, the film-makers may have been influenced by Cats. No doubt someone will provide a Cats/Avatar mashup for us in the near future. The relative hotness of cartoon Neytiri shouldn’t be a surrprise, as she’s based on the actress that plays Uhura in the Star Trek remake: Zoe Saldana.