I enjoyed it. I loved how its art style and overall color was fairly dim but it all blended so well together, it was very pleasing and interesting. Animation was about average, maybe above it a little bit, still fun to look at. Voice-acting was fairly good as well.
Here's my review breakdown...
+Nice art and coloring
+Pretty good voice-acting
-Little depth in the art
Overall, it definitely seems like one of those movies that has its own low expectations, but surprises the audience with it's very nice execution. I'd give it a 3.9/5.