The first quarter goal involved getting the game's tools and pipeline firmly in place, as well as "switching to the Unity middleware engine." The second milestone involved core game systems as well as the integration of a procedural terrain sculpting tool called Grome, the escalation system for PvE content, and plenty of art and programming work.
So what about milestone three? That's covered in the lengthy dev blog as well, and GoblinWorks' Ryan Dancey says that it boils down to "polish polish polish." He also mentions that the team is "solidly on track to hit our early enrollment goal." You can read the full entry at the GoblinWorks website.