When you look around swiftly in the Nether, it will take your camera a good second to follow suit. Best way to reproduce it is moving your mouse left-right as swiftly as possible, on a low-end device (on a high-end device, it's only slightly noticeable), while in the Nether.

I think the lag is felt at all times in the Nether, but is proportional to how fast you move your mouse.