I'm going to chime in here, even though I have only just come to this community as a newb. However, I do have a fair amount of experience on the stackexchange network, particularly in beta sites (both ones that eventually graduated, and ones that have languished in beta for years).
One aspect of site graduation that is sometimes overlooked is having a user-base with enough people with sufficient privileges to self-regulate.
A key aspect of this is having enough people vote, and, in all honesty, as a new member here, that seems to be something this site falls significantly short on.
A quick look at the most recent questions shows that the vast majority of questions are at 0 votes.
Out of about 4500 questions, only 22 questions have scores of 10 or more.
Out of 21 users with over 1000 reputation, 15 have voted less than 250 times, 8 of those voted less than 100 times, and 4 of those voted less than 50 times.
Voting, either up or down, is a very important, yet often-overlooked, aspect of a community's health.
I'm not suggesting you upvote low quality content, but I do believe there aren't enough votes being cast in general, and this is something that may slow down the development of your community. Generally, if a question is worth answering, it is probably also worth upvoting. Voting for other people's answers is just as important, if not more so.
Content doesn't have to be stellar to merit an upvote; just useful.
You've got pretty good site stats, for what that's worth, and the questions/day in particular is a good sign for a beta (in my experience, that's one of the hardest stats to hit "excellent" for). However, as Robert's blog post, linked in his answer here, mentions:
So from this point forward, the graduation date of a site will depend heavily on having enough users with sufficient reputation to properly lead and govern the site.
In my opinion, that's where you are hurting the most, and the lack of voting participation needs to be rectified in order to establish a community capable of self-governance.
