Microsoft changed the name of WPF/E to Microsoft Silverlight. This has to be the first time I've seen Microsoft go from a production-like name (WPF/E) to a codename (Silverlight). I guess they figured they needed something nicer than the usual jargon. To me, the name also suggests a stronger break between this web technology and the richer WPF

Tim Sneath has the full details here.

Also interesting to me is the lack of Linux support. When WPF/E was introduced a year+ back, the target platforms were Windows, Mac and Linux. I'll be interested to see if the idea of letting third parties handle the Linux port still floats.