Windows RT is the consumer version of Windows 8 which does not have the traditional desktop meaning all applications will be Metro or "Windows 8-style UI" apps.
Due to the different technologies employed, Windows 8-style UI apps are more akin to web pages than traditional desktop applications so a different approach must be taken when writing them.
As Mary Jo Foley wrote over at ZDNet yesterday:
"Microsoft is looking for developers to 'think different' when developing apps for Office 2013"
Macros and add-ins are being replaced by the new "could app model" for Office 2013 and the obvious desire from Microsoft is that all developers will ultimately move in this direction even if using Office in a "desktop environment".
Horses for courses
As the Windows RT variant of Windows 8 is being pitched as the "consumer" version of the new operating system (as opposed to Windows 8 Pro) the inference is that those using it are less likely to have complex documents requiring more business-like functionality so is this a case of horses for courses and ensuring you are using the right technology for your needs?
I can't help but feel that the response has been an over-reaction especially when considering the direction Microsoft wants to take with the new more cloud-based version of Office.