Joe Stegman, Director of Program Management on the Silverlight team, joins us to discuss Silverlight 4's Out of Browser improvements (OOB means you can run Silverlight applications on the desktop, outside of, well, the browser...). Of note, you can now interop with COM objects in SL4's OOB. We also touch on the the future of Silverlight and clearly define the distinctions/differences between Silverlight and WPF. When to use SL? When to use WPF?