8.1 - pretty much brings back the Win 7 Start functionality.
 
I do not believe there are any updates that do much for audio processing.
 
Some drivers seem to quit working in 8.1 for some things.
 
I am cheerfully running Win 8, and have NO immediate plans to jump on 8.1, until I get a better feel for its impact on my system.
 
Here is a link describing the top 10 features of the 8.1 update:
 
http://www.notebookreview.com/default.asp?newsID=6987
 
Bob Bone
 

You'll need to reinstall Soundforge if you want to run that in 8.1
 

I've updated and so far, no problems. I haven't used it much yet, however, but finally those stupid @$$ %#€$<?!?%^ (>%$$£<>#€%#€$} #%$%**+|{\€$^ Charms thingy dingys can be switched off when pointing the cursor in the top right corner!! I was about to roll back to Win7 but decided to wait and see what 8.1 would bring to the table. Check my sig, all my hardware works! And I think I actually like how it almost feels like an OS again.

And it also seems snappier and more stable. With the added wünderfeel I get from X3, this actually feels like another major UPdate in a matter of weeks!

But this is me and my system. I understand that this isn't the case for everyone.

To the OP, dunno what to check for but make sure your hardware is compatible. If not, replacing the parts that isn't is my only suggestion. It could be something as easy as an outdated FW hard drive. I have one that doesn't want to work with Win 8.1 and caused some weirdness. That's the problem with windows it seems, no right or wrong, only your system. Perhaps it will be better in a few updates (of windows) I sure hope so!

Best of luck!

Haven't been around here for a while and noticed the scary post title. Upgrade for me from 8.0 to 8.1 has been good so far. Was hoping for more feedback from folks with X3 installs on 8.1. Oh well... I just gave IE 11 a spin while making my online purchase of X3 and subsequent downloads. Will install X3 tomorrow and test things out. I'm not expecting any great problems since I don't think (correct me if I'm wrong) the Windows core has changed much from 8.0 to 8.1. Wish me luck!

Now that things have settled down with my update to Win8.1 I've got to say I don't think I've ever worked on a DAW and OS so well in tune with one another.

Win 8 sure was good, at least as good as Win 7 if not a little snappier. win 8.1 with Sonar Producer X3b is just flying. Made for each other.

soundtweaker
You'll need to reinstall Soundforge if you want to run that in 8.1
 

What version of Sound Forge are you on.
I'm on 9 and it's working fine. No need to re-install.

Vlada's issues with 8.1 are that once she went to it, she can no longer log on to the computer, as the USB drivers are not working since the upgrade.
 
After going round and round, she finally got to where she got Safe Mode to function, but she still cannot get past the Windows log on screen, due to the USB-connected keyboard not working.  So, she is at the moment dead in the water.
 
I thought a PS/2 connector expansion card might do the trick, but the only ones out there are either connected to the motherboard via USB, or the ones that connect via serial port are for a mouse not a keyboard.  I think reload is in her future - unless there is a way she could install Windows on a new hard drive, leaving the messed up one on another hard drive, then somehow getting the correct driver versions to overlay the non-working ones, then revert to the other messed up 8.1 hard drive.  I have no idea if that would work or not.  If it were my computer I would opt to reload everything to a Windows 8 level and take a system image prior to trying to go to 8.1 again.
 
It's all a long shot - she will most likely have to reload everything.
 
Bob Bone
 

Lets not forget all the hundreds of pieces of hardware gear that connect via USB with their own drivers. I have 8 pieces of gear in that category so updating an o.s. for me is worse odds than Russian roulette!
 
Put me in the "it aint broke don't fix it" category and for me win7/64 decidedly ain't broke.