Of course with all major Operating System updates, you'll want to be sure your applications work before upgrading. Rest assured, NovaBACKUP 14.5 functions just fine in (most) of our tests on Windows 8.1 (see the photo below). However, if you want to be 100% sure, we are currently in the process of beta testing and certifying version 15 of NovaBACKUP which tackles any of the minor issues we've seen so far and you can sign up for free!
Our NovaBACKUP team generally likes to refer to themselves as a, "Windows Shop" and as such, we're excited to welcome Windows 8.1 and Server 2012 R2 to the world!