I'm seeing weird, significant framerate drops in certain chunks for no observable reason. The framerate drop ceases instantly when moving out of afflicted chunks. The direction you are facing has absolutely 100% no influence on the framerate drop and as such it's also not something terrain occlusion seems to prevent from happening. In a way it almost looks more like something like entity lag because of that.
Example coordinates: (1164,-96) in seed -1430031728
Addition: the framerate drop seems more significant in my 'older' survival world than the newly created creative copy of the world (I can still notice it though). I'll see about attaching my survival world also.