I did the upgrade months ago to the Win 8.1 Preview on an Acer tablet that was given to me a year ago by a class action settlement. It came preloaded with Office 2013. There were no problems with the upgrade and I liked W8.1P better than W8 (my other computers are Win7 now, with just one XP remaining).
A few weeks ago I upgraded to the actual Win 8.1. I lost Office 2013 and since my tablet was a reman unit, Acer doesn't support it. No, I hadn't backed up Office since the upgrade to 8.1 Preview had gone so well.
I suppose I COULD attempt to regain Office 2013 from the reman company but found it simpler to just d/l and install Open Office. For the amount of Word and Excel work I'll do on the tablet (much less than 1%), Open office will be fine.
I had to reinstall Apps that I got from the Windows Store, but it was just a matter of clicking an icon to reinstall, as the apps I had were recorded.
For your upgrade, just you shouldn't have any problems but I wanted to share the only problem I had.
Phil