Watched the Giant Bomb quick look of the beta recently and while it came across as somewhat appealing, it didn't look particularly compelling.
The story/lore stuff (inc "that wizard came from the moon") is pretty repugnant.
I think it's how small and meal piece the missions are that turns me off it. I would have liked more hand crafted level design than re-using the same environment over and over for missions. Guild Wars 1 did this really well and still kept the same mmo mission structure that Destiny has.