Yesterday I went to the SharePoint 2013 DevCamp in Redmond WA http://www.devcamps.ms/office
It was a great 2 day DevCamp focused on the development of SharePoint 2013 Apps for the Office store. The first day we did an overview of the SharePoint 2013 new App development model and reviewed the development tools.
The second day, we developed our own SharePoint 2013 app. In my case, I developed a SharePoint Hosted-App that got information from a Windows Azure Rest service using oData and oAuth. I was able to develop the solution in a few hours and deploy it to my Office 365 SharePoint “Napa” developer site.
You can get the DevCamp PowerPoint presentation and code at: http://bit.ly/Apps4Feb
Also, I recommend to get a free “Napa” Office 365 developer account at: http://msdn.microsoft.com/en-us/library/jj163980.aspx