It's a tricky question.
This is NOT a site review, but a personal observation having followed this subject on the network for some time.
I think we've done a better job at scoping out something fundamentally more useful as a site. The formative question is whether we have a suitable audience to actually build out this space. But that has to happen here and now; they won't just show up later.
Stack Exchange is billed as a network of practitioners helping their peers solve everyday problems. Unfortunately, a large percentage of the questions being asked here sit squarely in the curiosity-seekers space. Questions mostly wallow conspicuously in played-out subjects which "real" AI researches have stopped asking a long ago — Is this AI? What does concept mean? When are we going to get there? When is AI going to do {x}?
I won't pass judgement on whether we've given up on actually building a peer-review site. I talked about some of this in no artificial intelligence in Area 51.
There are certainly at least a few very knowledgeable people in this community — actual researchers working in this field — but there's a bifurcation of posts from folks with active experience and someone just showing up with whatever they find in a cursory Google search. The problem is that the community either doesn't know the difference, or doesn't care to vote up one over the other. It's hard to fault anyone for trying valiantly to get something going here, but watching something from Wikipedia being voted on with equal alacrity is somewhat… discouraging.
Have we brought something new to the network?
Probably. Questions here don't generally fit elsewhere.
Have we created something useful?
Hard to say; that's a big question for the final review.
Does this a address a peer group prevalent in this space?
That does not seem likely — If you read Asking the First Questions, I suspect that ship will have sailed by time we reach public beta.
Have we improved the Internet in general?
My suspicion is the lack of true peer review in this space will make most of what is posted here about status quo with what you can already find elsewhere. That is by no means certain; that is just my observation.