I rushed to this blog out of panic from what I read elsewhere. Having seen the W8 demo I have to say that as a .net developer of enterprise apps I'm not getting ready to jump ship yet. First off  I can't see any way MS is going to dump .Net, but I fear for Silverlight and WPF. I havn't used them in earnest yet so I'm not going to bother starting now. (I always hated WPF anyway.) For serious apps,  Html 5 and Javascript are only going to affect the View layer. The control layer and data access logic piece of the model layer will remain c# and VB. For throwaway consumer apps, HTML 5 and js will do the job but like some else said it is basically Vista Gadgets reborn.

I think it is right to have a consistent user experience across different platforms but designing the desktop UI primarily for touchscreen is a mistake. The majority of the world's office workers are still going to spend all day in front of vertical monitors; The mouse rather than the finger will remain the pointing device of choice, and tiles are no so good for running loads of complex business apps at the same time.