I have been interested to note that some of the criticisms of the movie I have read that were not wholly enthsiastic had reservations specifically because the rats were sufficiently realistic to make the reviewers squeamish. Well, I guess if that's your hang-up there's no getting around it, but I think that just because you were frightened by "Willard" as a child you should not give this movie full marks for artistic integrity.
True, Remy (the cooking-enamored rat) is not Mickey Mouse. He's not even Jerry from Tom and Jerry. He doesn't wear clothes. He runs on all fours (mostly). Although he understands human speech, he can't talk to humans. (it is established that the humans only hear squeaking--). Remy has fur (OK, blue fur) rather than a smooth coat of paint, and when he gets wet (which happens frequently) he looks like-well, a wet rat. When doing ratlike things, Remy MOVES like a rat. In one shot, where he is panting, his abdomen moves in the right places, so he even breathes like a real rat. Nevertheless, Remy is a very engaging rat, and very cute when doing human things like cooking.
The story of how Remy partners with Linguini, the hapless "garbage boy" who is clueless on cooking, works out cleverly and with a lot of fun incidents. The jokes are fresh and not cliched. The story has some genuine tension and a few good plot twists. The animation is fluid and the background design beautiful with recognizable Paris landmarks beyond the inevitable Eiffel Tower. Both Georgie and I, having worked in food service, agreed that the story included some home truths about the restaurant industry (including the kitchen crew's checkered past--). We absolutly enjoyed it all.
Pixar has done its usual job of levening experienced voice talents, notably Patton Oswalt as Remy and Lou Romano as Linguini, with veteran actors like Brian Dennehy, Ian Hom, and Peter O'Toole, with good effect. Janeane Garofalo brings fine passion to the role of Collette, the only female role in the film. (All the rats are males as well, which is a bit weird when you think about it--.)
Although it is animation, the story is a bit sophisticated for young children, but is a very family friendly film since there is no sex or bad language, and an actually uplifting story, although there is fairly intense cartoon violence, expecially when the humans are chasing the rats.