Macros, Add-Ins, Forms, and other custom programs written by third parties. For all these you will need a PC or a Surface Pro.
SkyDrive Sync Integration. We?ve already written a post on this, check it out for details: SkyDrive Offline. It is supposed to be fixed with the new 8.1 version of Windows RT but it is not yet released.
Equation Editor 3.0. This is the legacy (older) equation editor used in previous versions of MS Office. You can still view the equations but you cannot edit them. However, a new feature for editing equations is included in PowerPoint RT. So, you will be able to create new equations on the RT.
Slide Library ActiveX Control. SharePoint Slide Library toolbar is not supported but you can use the Slide Reuse pane instead.
Legacy Media Formats. You will need to use modern video media formats like H.264 and Advanced Audio Coding instead.
Flash Video Playback. No videos designed for Adobe Flash Player can be inserted or played back in PowerPoint RT.
Recording Narrations. You will not be able to use the Record Narrations feature on your Surface RT. Again, for those you will need a PC.