Another nail in the coffin for Metro - Metro IE does not support ANY addons or plugins.
Apparently this is a design decision but it means you can't use Flash based sites in Metro and also it doesn't even support Microsoft's own technologies like Silverlight!!
No plugins/addon's also mean no in browser document support (eg. PDF).
This is going to be almost as silly a iPad emails where you can't open some extension types!
OK you can use IE normally on the 'legacy' desktop but what an arbitrary and silly restriction to piss people off in Metro!