Hey there and Happy New Year!
I asked before about success stories with Windows 8.1 update. I personally had horrible experience on my other newly built computer when updating from 8.0 to 8.1, it lost USB support and I ended up reinstalling Windows. By doing this, I learned that 8.1 update is not reversible- it would not do back to 8.0 via system restore from last best known configurations, system refresh or any other method- it is permanent.
 
My music computer is still 8.0 and it bothers me. I want to update, for no valid reason. It just that I am getting so used to 8.1, I start feeling difference and to me 8.0 is lagging and things are not in the right place, compared to 8.1. But everything is working (other than Maschine controller when connected during the boot).
Presonus told me they are compatible. Not sure about Motif XS MIDI driver. Motu MIDI should be compatable, Roland V-Synth and Fantom G- about to find out...
 
I am concerned with my VST plug ins. I have Komplete 9 Ultimate, and all together Sonar counts 195 plug ins at this time. All my plug ins are paid software synths. I am afraid- all of them will go out of order or disappear from the list- I hardly remember what should be on my list. Can IK Multimedia soft synth handle 8.1? They are old synths. Feel free to talk me out of it. Thank you.
 

Just to give you a confirmation, the MOTU MIDI drivers work fine under 8.1. I have 3 midi express 128 interfaces hooked up with no issues.

Thank you, this is what I have as well. Good.
 
It would help to understand what exactly Win 8.1 updates. Does it do anything to the file locations? I know that my Yahoo and Norton toolbar stopped working, (because it is 32 bit or what ever) and only few days ago Yahoo fixed their. If it only updates Metro interface, then we should be fine, but I heard it was something about ASIO driver...
 
 

I didn't have much trouble updating.  I'm not that thrilled with the update but it wont hurt that much if you like 8 to begin with. Just be sure that you have 8.1 drivers for all your gear. 

If it ain't broke, don't fix it. I know I'll need Windows 8 at some point, but Windows 7 does everything I need to do except enable touch for Sonar (which is why I will upgrade eventually).

i couldn't upgrade. some driver error that even 2 ms techs couldn't figure out how to get around or what it refers to. must have wasted a full week over the course of 3 months. tried all the advice online.
 
i'm on 8 until ms can deliver a better installer for 8.1 or the 8.2 installer is more forgiving...

John
Just be sure that you have 8.1 drivers for all your gear. 

+1 This is the biggest thing to verify. The "non-reversible" part of Win8 made me back out of any notion of upgrading beyond Win7 for now myself.
 
I have not forgotten Vista enough to trust MS yet....

I've been running Windows 8.1 since it came out with no problems......

From the horror stories I've heard I'm keeping on win8 and not updating it eveeeeer!

Yup the horror stories are always louder and far more scary than the success stories....