maximumpower
FWIW I just installed 8.1, loaded up a demo project and heard the audio through my m-audio Profire 610.

Sorry, meant to reference this post. 
 
Hey, this is my first post and I'm dying to know how you got the Profire 610 to work with Windows 8.1. I have it connected to my PC and I installed the latest drivers for the Profire, but when I launch the software it says the hardware cannot be found. Any help would be MASSIVELY appreciated.
 
Thanks,
Ben

I updated from 8 to 8.1 on my Toshiba Laptop several months ago. As stated earlier the only hiccup I got was having to re-register Addictive Drums. Everything is running smoothly. I did the fix to boot to the desktop instead of the charms window and yes it does return your Start button but you have to right click it to see the options. Left click toggles between the desktop and charms view. The fix to boot to desktop fix is a video on YouTube or just search or Google how to do it.

mudgel
I've downloaded the 8.1 update now but after it reboots i get an error saying inable to.complete update and going back to win 8. Tried 5 times with same error.

I had this problem when I downloaded windows 8.1. I couldn't get the windows 8.1 to download. After searching google I found a way out.
I had to go to the Command prompt and type in msconfig. Then I had to go to services and check the box that said Hide the microsoft services and then I had to go to the startup tab and disable all other startup programs. Then I had no problem downloading windows 8.1 . After installation was done I went back to msconfig and started the startup programs again and unchecked the hide box. Everything is running great now. 

I am used to being one behind the ball.. as i have hardware synths its win7 until this PC dies, then it will be win8.1 (probably after after win9 is released...lol). so in a few years there should be drivers around for everything i have

Everything went smooth for me.  Up and running.  The only issue that I had is with Addictive Drums.  AD is asking for me to redo my authorization key.  I am usually really good at keeping all my serial numbers and keys recorded on a log.  Unfortunately, I can't find the key for AD. 
 
I have an email into support.

Your AD serials etc will be in your AD account not Cakewalk.

The serial is actually at the Cakewalk account, the Product Key, I believe is from AD.
 
This was the response I got from Addictive Drums....I haven't been home to try this out, yet:
 
If AD asks for authorization, it's probably because either the Online Installer
or AD generates the wrong Computer ID. Usually this happens when either the host
(Sonar) or the Online Installer is run in compatibility mode. Right-click on the
Online Installer icon -> Properties -> Compatibility tab. Then deactivate
Compatibility mode if enabled, then run it to fix the authorization. Do the same
for Sonar.

Running 8.1.1, all updates
 
Using EMU 1820m with 1616 beta driver.
 
So far seems a bit more stable than with windows 7, and 8.