AlexBobbs (a self-described American animation freak): This movie was cool. The story was surprisingly unpredictable and the characters were funny. Oh, and forget everything you know about Disney cartoons. In this one, the nerd gets the girl, there is lots of violence (not graphic though), there is no singing, and the whole thing is drawn more akin to anime and the Batman animated series than your usual Disney fare. The action sequences were tense and at several points I had to restrain myself from shouting out "Holy Shit! They're screwed now!" (thus corrupting all the little kids in the theater). This movie also has some of the coolest Jules Verne contraptions ever and really hot animated chicks. The only thing I didn't like was that the movie feels a bit rushed. Some times I wished it would slow down and fill me in on the details, because I felt like there was a huge iceberg under the tip I saw. Another twenty minutes (Which would make this a really long animated film) would have made "Atlantis" really great, but I'll take it as it is because it's so much fun. BTW, I've never heard of Nadia, so whatever
KurtDresner: I agree on the rushed bit, the movie could have slowed down in several parts. Other than that I think it was quite enjoyable.
TimBuchheim: I liked it. I too agree that this movie felt rushed at times, but the animation was great. There was a bit of a "Wizard of Oz" effect as the animation switched from the hard-edged, drab style used for New York to the softer, more vibrant and colorful Atlantis style. A bit more subtle than the bw->color of Oz, but cool.
DuctTapeGuy: I think one reason the movie felt rushed was that the writers did an amazing job with characterization. In a very brief span of time you really get to know all the major characters (especially the crazy digger guy, who is totally awesome), so you spend some parts of the rest of the movie wishing you'd get to see more of them. Overall, this is a great movie.