SSD installation ( the way which worked for me) , installing directly to SSD was dropped constantly an error after the first rebooting, so

-downloaded the ISO from
-wrote it to an empty DVD (from USB it not worked) with Windows 7 USB/DVD Download Tool 
-installed from it to a non SSD drive (created an empty partition used its format tool )
-finally migrated it into the original SSD dirve with Paragon Migrate OS to SSD™ 4.0 
 
now I'm happy :) 

For those who want a clean install after the upgrade this site has some good information.
 
http://www.forbes.com/sites/antonyleather/2015/07/30/windows-10-updating-reinstalling-and-activation-guide-essential-advice-to-avoid-problems/
 
There is a link on the page to download a utility that will show you the product key so you will have it during the reload.

For those that have upgraded or considering upgrading, the Windows 10 forum has lots of good info and help.
www.tenforums.com
 
I have my 8.1 upgraded and after Roland got their drivers upgraded everything is working OK, including my VST add-ons such as Ozone 5. iLok is working OK.
 
When I record, I disable the NIC (Ethernet adapter) so I'm off line.  The prevents possible interference to Sonar from network activity.
 
I'm in the Windows "Insider program" and have had Win10 Preview (Beta) versions for quite a while.  The only thing that put a kink in things was my Roland Studio-Capture and Octa-Capture installed OK in an early Win 10 Preview version but in the final 10240 version they would not install.  I had been going around "fat dumb and happy" assuming they were OK.  Apparently the early Win 10 Beta versions were more Win 8.1 than 10 and Roland drivers did install and work.  I never checked them after that until 10240 version (the "final" version).
 

Are there any other audio optimizations to perform on 10? I had a lot of things tweaked in 8.1 and 7 that did greatly improve the performance of my audio interfaces and the computers.  I am very pleased with the performance so far in 10!

Noel Borthwick [Cakewalk]
One "optimization" you might want to disable is this one.
By default Windows shares your windows update downloads over the internet (like bittorrent). For a DAW you probably want to turn off this behavior to prevent unwanted background internet activity. I've set mine to only share it on my local network, not the internet.

Oh and if you want to stop Windows update :
start a CMD app (Windows key + X - Command Prompt ADMIN) then type - net  stop wuauserv  to restart same command except replace stop with start

By the way, you don't need to have the windows key to activate it. After doing the update process from a previous version, you can do a clean install as mentioned earlier. When the screen comes that asks you for the product key just hit skip for now. Windows will activate itself after finishing the installation based on the update version you did earlier.
 
Have fun