Interesting, I'm sure the opposite was said during the keynotes, but I'll take that as a more authorative resource. Still the majority of the really neat stuff like charms and contracts will presumably require appcontainers so I'm not sure there will be quite the same benefit (although .NET developers will probably be glad not to have to PInvoke quite as much).
I went to a post BUILD event last night and the same discussion was had there, too. It seems to still be confusing even with the evidence on both sides.
That said, if WinRT is as awesome as it seems, it will almost have to end up being callable from everywhere...