Instead, there is the criticism that Microsoft is not enough like Apple (and a focus on personalities).
When manufacturers don't see a way to build and sell dual screen tablets at a profit, Microsoft won't sell much of the software to run them. It is not as if Microsoft doesn't have the enough experience as a hardware provider to evaluate the economics of going it alone versus partnering with the electronics industry. And partnering with the electronics industry rather than competing as a manufacturer has - with the exception of the XBOX in a market dominated by proprietary hardware - been a highly successful course.
Finally, it is not as if the design decisions underlying the courier are dead - a viable dual screen tablet is still as plausible today as it was when the iPad started shipping and there is no reason such a device could not run with a Metro interface or that the technology developed as part of the Courier project could not be incorporated.
What was killed was a project which required forking the Windows roadmap in ways analogous to past Microsoft decisions and which led to Windows Mobile becoming a dead end overnight - never mind that a mobile device without email probably would have been stillborn.