In the Minecraft snapshot 14w08a, seamless teleportation was added.
Showcased here in this map: http://www.minecraftforum.net/forums/mapping-and-modding/maps/1556313-14w08a-antichamber-10-000-downloads

You cannot tell at all when you are teleported, making it a very interesting map, and this adds a lot to the game.

However, in the latest pre-release of Minecraft seamless teleports no longer works, as the screen glitches every time you teleport. (Compare the map in 14w08a and pre3 to see what I mean)