UPDATE 7:45 p.m., 2 May 2012
The female was off the eggs for a few minutes just moments ago. There are no chicks, yet, and there are no clear signs of hatching. The adults are likely responding to the chicks, which will begin making vocalizations when they are close to hatching (yes, from inside their sarcophaguses).
If you have been checking in today, it is apparent that something is happening. The adults have not just been sitting on the eggs in their normal posture, but have been hovering and often looking down at the eggs with high levels of curiousity. The still frame below is not untypical for today. I have yet to catch a peek of anything definitive. You may want to pop-in more often, now, and if you end up seeing a chick, please provide a comment to let everyone know.