Since my baseless speculation post on achievements, there have been some notable blue forum posts on the topic. These answer a few of the questions surrounding the system. To summarize:
- Achievement Points are NOT Spendable.
- Achievement Point totals are PER CHARACTER, not account-wide at launch. As a result, launch achievements are limited to things that a single character can accomplish (i.e. we cannot have achievements like "level every class to 80", "complete X class-specific quest/activity", or "have every profession maxed out somewhere on your account").
- On launch day, everyone will have to go kill every boss from Van Cleef on up again if they want the points, because many achievement categories cannot be retroactive. This will mean that many people who actually completed level 60/70 raids will not be getting achievement credit for it. On the flip side, this might provide a greater incentive for "old world raiding", since you can get the points and Armory status even though you don't need or want the rep/loot.
- Based on another post on the topic, it appears that the system CAN track "have you completed X quest (or unveiled Y part of the map)?", "is your reputation with X exalted" and "do you have X item in your inventory" I.e., stuff that you cannot repeat, or that the game can specifically conclude that you must have accomplished by looking at your character on launch day. If you're considering working on achievements now so that your character's score will be nice and high on launch day, these are the areas to focus on.
Overall, the answers we've gotten so far are encouraging. It's too bad they can't stealth patch in the tracking code now, but I guess that's the downside of adding this system in to the game four years after launch.