In creative or survival, Minecraft has a large amount of lag. This wont stop until the world is completely loaded. Also, while looking around, some parts of the world will have lag while others will not. It doesn't matter what biome/world type was chosen. This issue was not present in 1.5.2 and has just begun after I updated to 1.6.1
Related issues
Comments
migrated
I think this is because the chunks are generating. Pause the game and wait for them to generate.