Biomes in newly-generated worlds now inexplicably have very large, square chunks between them and another biome. This isn't a chunk error, because the blocks within the square regions are legitimate (instead of a long pit all the way to the Void).

For instance, I had a plains biome with shores that had square "bites" taken out of it (like at an old-new world boundary after the last major biome change).

Another instance (and this is the screenshot), the Extreme Hills biomes seem to be bisected neatly by the sand of an adjacent beach.