Roxio Buzz is a viral video editing and upload application written in WPF.  This app makes it easy to perform simple video edits, transcode and upload the video to a sharing service.  Just yesterday Roxio announced support for uploading to Silverlight Streaming and released a beta version.  This is a very handy application and the visuals are nice, but the installer took way longer than I would have expected.  Probably 4x-5x longer than Blend, which is the WPF app I consider to be the benchmark for installation time.