World of Warcraft: Wrath of the Lich King Interview

IGN's WoW Vault has tossed up an interview with World of Warcraft lead designer Jeff Kaplan about Wrath of the Lich King. It is available in audio format, but they also sum the main points up in text format.
Another feature being introduced in WotLK is Achievements. In effect, these are a player's own personal record of all the content he or she has achieved in the game. At any point in time, you could pull up this list of Achievements and examine them through your UI (user interface). While most of these are for your own personal sense of accomplishment, some do grant displayable titles and others give you cosmetic rewards. For example, if you complete all the PvP achievements, you unlock a final one called Battlemaster, which grants you a title that you can display above your character's head. As far as rewards go, an example would be unlocking the 25-tabard achievement (meaning you collected at least 25 tabards), which earns you a new and unique Tabard of the Achiever.

One fun achievement that I may go for is the one that grants a unique pet for collecting all the available pets in the game a pet skunk called Stinker.

Unfortunately, not all achievements will be retroactive. Only those that involve quest completion and collecting things (ie. things that Blizzard can easily track) will be granted automatically once WotLK goes live.