The addin development methodologies have changed sizeably in Orcas. However, to use this COM  based control, you still have to develop your form region within Outlook. You can then import it into Orcas and handle the top level event for the scheduler. If you have built a replacement form region, this scheduler will override the default scheduler and you can play around with the events.

 Create an appointment

 Hit the developer tab and create a new form region

 Hit the contol toolbox and browse to add the page control

Now that you have the page control on the form region region, you may save it and import it from within Orcas. If Outlook has been configured to pick up .vfb files from a particular location, once you add a recipient to the page control, you should be able to automatically see the free busy status. So, do not script your own parser unless absolutely neccessary.