Since the late snapshots of 1.7 and the addition of "Super Secret Settings" anti aliasing has become impossible with Nvidia graphics cards. Due to this problem, edges of textures and blocks are very jagged and distorted. In Minecraft's "options.txt" if you disable "fboenable:" by setting it to false, anti aliasing will work again however, Super Secret Settings will black out your entire screen and the magic effect found on potions and enchanted items can take up an entire inventory slot.