In terms of quantity, we're doing fine. A private beta should produce about 100–200 questions, and we already have 84 as I write, 63 of which are not closed.
But quantity is not everything.
Almost half the questions are tagged license. Not all license-related questions have this tag, so more than half of the questions on the site now are about licenses.
I'm not seeing OS.SE as a distinctive site. What does this site cover that Programmers doesn't?
If OS.SE is to succeed, it needs to work on carving out a scope that is useful to its intended audience and that is not better covered elsewhere.
The private beta should be a time for expert questions. I'm not seeing many expert questions. Our most voted questions (e.g. 1 2 3) are topics that have been covered many times on the Internet. Many questions — in particular questions about licenses — are novice-level. Novice-level questions have a place on Stack Exchange, but not really in a private beta. If the private beta doesn't lay the grounds for expert content, the site will never become attractive to experts.
If OS.SE is to succeed, it must not bore experts away.
I see a lot of answers that do not demonstrate a solid knowledge of the topic. Again, licenses — OS.SE seems to convey the uninformed programmer's view, not the IP lawyer's view.
If OS.SE is to succeed, it must produce better answers than what can be found elsewhere on the Internet. Not distorted summaries of a poorly understood blog post.