After upgrading my Surface RT to the RT 8.1 Preview - which took less than 30 minutes and was quite smooth (through the Appstore, nothing really to do but wait..) I now have a wonderful business device running instead of the black brick I had an hour ago.
Why? Because Outlook is installed and running as part of the upgrade. Now I have a lightweight, fully functional PC that runs all the Apps I need on a daily basis.
Livetiles for Office would have been nice - but oh well, can't have everything. For Windows RT this is a huge update (for Windows 8 Pro nobody needs it - the Startbutton is the biggest joke, some of the other tweaks are nice, but nothing worth running the Preview or to update immediatly). Outlook is the real differentiator.