TXAA is leveraged throughout the entirety of the game, and DX11 Tessellation is used in the winter season of gameplay.
NVIDIA has released a new video for Assassin's Creed III, showing how the game takes advantage of specific PC technologies to enhance the overall gameplay experience. TXAA is a new film-style AA technique designed specifically to reduce temporal aliasing (crawling and flickering in motion). In this video, you can look at the buildings, the ropes on the ships, and the foliage. Without TXAA, you can see crawling, most vividly while the character is in motion. When TXAA on, the crawling and flickering practically disappear.
Also, in Assassin's Creed III, tessellation is used to smooth out the footprints left in snow by the player in heavy weather situations. Tessellation dynamically produces more polygons in a scene to create a more realistic rendering compared to standard methods. You will experience a lot of snow during the game and this technology enhances the realism and fidelity of your experience.