A new ArenaNet blog entry popped up this evening and surprised everyone with details on sweeping changes to major elements of GW2. The list is long and varied, covering a wide range of game elements. For example, energy potions, planned game items that were debated fiercely among the fanbase, have been done away with -- in fact, skills no longer cost energy. In place of the energy potion button you'll find a new, energy-based dodge mechanic.
Skill acquisition has completely changed for several reasons. According to developer Jon Peters, the previous method "wasn't helping teach people the game, it didn't fit with how skills actually worked, and it didn't carry over the fun collection element that made the original Guild Wars unique."
There are several more changes to hear about. Jon details them -- and gives new details on the demo -- in the full ArenaNet blog post.