A brief summary of the enchantments added by Thaumcraft and their uses, as some may have changed:
Repair - Causes items to slowly repair over time. This is a two-tier enchantment, and the higher tier works faster than the lower. Due to changes in how magic works, this enchantment is no longer impacted by proximity to nodes. May be used on weapons, wand foci, and tools, excluding shears. This enchantment drains vis from wands in your inventory to repair items and the cost of the vis is determined by how important or valuable the item is.
Haste - Bonus movement speed. Can be applied to the Thaumostatic Harness to bring its flight speed up to something useful instead of its default crawl. This is a three tier enchantment; each tier obviously grants a greater speed increase.
Old Focus Enchantments:
Formerly, wand foci were enchanted like tools or armor, including the following options. As of Thaumcraft 126.96.36.199, the following are no longer item enchantments. Instead, foci are upgraded with the Focal Manipulator.
Potency - Increases the strength of the cast. This is a three-tier enchantment, and each tier increases its power. This enchantment is only suitable for wand foci, and its effect varies by focus, e.g., the Equal Trade focus will swap out a larger group of blocks with a potency enchant applied to it. The higher the enchantment level the more vis the spell costs however.
Frugal - Reduces the Vis cost to use a focus. This is a three-tier enchantment, and each tier offers greater cost reduction. This enchantment is only suitable for wand foci.
Treasure - Increases yield from blocks that drop items rather than ore, e.g., diamonds; it is the equivalent of a fortune enchantment. This is a three-tier enchantment, and each tier increases the chances of a block yielding extra resources. This enchantment is only suitable for wand foci.