Since it was first announced, there have been rumblings about various restrictions that would be placed on the ARM version of Windows 8. Most of those concerned plugins and desktop experience, but one particularly troubling rumor was that Microsoft would lock down Windows 8 devices so that users wouldn't be able to replace the stock Windows 8 installation.
Although the Windows 8 hardware requirements detail a method for users to sign their own operating systems for installations, it turns out that the ARM device requirements actually prohibit use of this method, saying:
"On an ARM system, it is forbidden to enable Custom Mode. Only Standard Mode may be enable. Disabling Secure [Boot] MUST NOT be possible on ARM systems."
The impact this will have on some users is pretty significant, as unless the security is broken through brute force, owners of ARM-based Windows 8 devices will only be able to run Windows 8 and the Metro interface. Microsoft's Tony Mangefeste cites "Microsoft's philosophy to provide customers with the best experience first" as the reason for this decision, but that doesn't really seem to be a valid argument.
It is true that most users who buy Windows 8 tablets will be perfectly happy with Metro, and enjoy the user experience as well. However, the few that want to change things don't need Microsoft to manage their user experience, and as such won't like the lockdown at all. Despite these problems, I'm still very excited for Windows 8 hardware itself, it's just disappointing that it looks like Microsoft won't let users customize the hardware they own.