I upgraded to Windows 8.1 this morning and had relatively few problems.
 
I ran the Sonar X3 demo with all the tracks enabled and the mix-down track muted.
 
Seems to be OK so far, but I have lots more things to test.
 
 

I will upgrade over the weekend. I read a review that they have brought back the start button. Does it mean that Classic Shell and other start button apps are not required anymore? I would love to remove classic shell if it's not required at all. It's takes only 5MB of RAM so I am not gonna get any boost but I would like to keep the system as lean as possible. I installed it just for the taskbar and start button.

arachnaut
I upgraded to Windows 8.1 this morning and had relatively few problems. I ran the Sonar X3 demo with all the tracks enabled and the mix-down track muted. Seems to be OK so far, but I have lots more things to test.  

What soundcard are you using with it?

When I looked there we're no 8.1 drivers for my UA-101. I've seen other folks saying their soundcards have stopped working.

Can't upgrade here.
 
My CPU is not compatible!
 
Wish I'd known that before I bought 8!!!

good news. what version of win were you upgrading from?
 
i upgraded my internet laptop, running the win 8.1 preview, only to find that all my programs have to be reinstalled. not a big deal, as i only have a few that i really need, but no warning, just gone. (the programs are still on the hard drive, to be clear, and in some cases i have the installers, but win 8.1 doesn't know them.)
 
my music pc is running win 8. to reinstall everything on that one would be not fun. hopefully win 8 -> 8.1 keeps your programs intact. anybody know?
 
for now, that pc stays on win 8.

jeffb63
Can't upgrade here.
 
My CPU is not compatible!
 
Wish I'd known that before I bought 8!!!

Aren't the system requirements for 8.1 the same as 8.0? I thought I read that somewhere.

satyatunes
I will upgrade over the weekend. I read a review that they have brought back the start button. Does it mean that Classic Shell and other start button apps are not required anymore? I would love to remove classic shell if it's not required at all. It's takes only 5MB of RAM so I am not gonna get any boost but I would like to keep the system as lean as possible. I installed it just for the taskbar and start button.

The Start button is there but the Start menu is replaced with the new Start screen.

My quadcapture driver isn't compatable? I have no sound and have to wait till they release them now as I can't roll backl to 8!!!! Darnittall!!!!

I was upgrading from Windows 8 Pro with Media Center.
My soundcard is a Firewire Saffire Pro 14. I updated it to the Mixcontrol 3.3 firmware before the upgrade. I also updated my WiFi interface.
 
Two things did not work for me: PerfectDisk 12.5 (a superb disk defragmenter) and Acronis 2013.
I was able to image and restore using Acronis 2013, but it would not mount the image as a drive - a feature I found useful.
So I bought the Acronis 2014 update. It was a very smooth install, unlike the previous few Acronis updates.
Perfect Disk is due out October 1 - so they are running quite late.
 
I also had a bit of trouble with the Documents folder - I 'Locate' it to J: and it ran into some problems.
I think I have these troubles fixed now, but there are lots more things to test.
 
I didn't have any trouble with Live or Reaktor either so far.

DaddyV
My quadcapture driver isn't compatable? I have no sound and have to wait till they release them now as I can't roll backl to 8!!!! Darnittall!!!!

http://www.roland.com/support/article/?q=downloads&p=UA-55