The "alpha" killed a lot of my interest in the game. I'll probably pick it up, but this isn't at all the kind of game I was looking for.
The "open world" part is just a larger level with respawning collect/kill quests. The whole world felt really lifeless. Unless the gameplay present isn't representative of the end product at all (highly unlikely), then I feel it's going to get boring really fast. I was going into Destiny as a PVE game primarily, since I have no interest in competitive console shooters. It looks like this game is going to be PVP first with some barebones PVE grinding added on.
On the positive side, this game looks stunning. Absolutely stunning. The first words out of my mouth when I booted it up were, "this is next gen." The character creator is awful, but it's not too big of a deal (never depend on Bungie for human models). The lighting and skyboxes are breathtaking.