Geo524 - Are you able to use the 1.9b10/3.2.2 drivers and work in Sonar?  I couldn't get it to work at all.  I noticed you're using an AMD processor.  I'm using an Intel i7.  I wonder if the chipset I have is an issue.
 
Riojazz - I noticed you're using an i7.  What motherboard are you using?

I now have the 1.9b10/3.2.2 set working with Sonar, but I'm not sure what I did.  However, I have to use twice the buffer size than I did with the 1.8/2.5.1 set to play back the same project without pops or clicks.

aspenleaf
Geo524 - Are you able to use the 1.9b10/3.2.2 drivers and work in Sonar?  I couldn't get it to work at all.  I noticed you're using an AMD processor.  I'm using an Intel i7.  I wonder if the chipset I have is an issue.
 

 
Hi Aspenleaf. Yes. Everything is working. Just a little more CPU intensive than when I had the 1.8 drivers. Glad you were able to get the beta drivers working. I would seriously contact Focusrite and hound them about releasing an official win 10 driver for the 18i20. Power in numbers. The tech I am in touch with is sympathetic to the frustration this is causing and said he is going to foward my emails to the developmental team. It's a shame cause the 18i20 is really a fine interface.
 

I will continue to work with the Focusrite tech and hopefully they can work this out.  When I first ran into issues with Windows 10 I reinstalled the backup I made of Windows 7 and reinstalled Windows 10 as a dual boot, so I can keep working in Windows 7 until Focusrite could work this out.
 
I agree that the 18i20 is a fine interface.  I have no plans to replace it, but I think Windows 10 isn't ready for prime time.  I'm having a slew of other issues on my laptop getting it to work with my printers and scanners, so I had to roll back to Windows 8.1 on that machine.

Good idea to install Win 10 as a dual boot. I'm not having any major issues with the beta drivers so I can wait as well. 
 
Now I'm wondering if I should install our new printer? All the computers in our household are running Windows 10.

aspenleaf
Riojazz - I noticed you're using an i7.  What motherboard are you using?

In case it helps, this is what I have in my home-built rig:
 
CPU:    Core i7-4790K
Motherboard:    Gigabyte Z97X-SOC-CF Socket 0
Nothing overclocked

I had some issues when I first upgraded to Windows 10.  I sent an email to Focusrite and a couple of days later they sent me a link to a different (beta at the time) version of MixControl.  It fixed my issues and has worked fine since.

townstra
I had some issues when I first upgraded to Windows 10.  I sent an email to Focusrite and a couple of days later they sent me a link to a different (beta at the time) version of MixControl.  It fixed my issues and has worked fine since.

Are you running 1.9b10/3.2.2? 

Have any of you run the Latency Monitor that Focusrite techs ask you to run?  I'm getting very strange results.  It says my computer isn't capable of playing audio, and it shows my i7 3.4 Ghz cpu as running at 2.2 Ghz, even though I have disabled the cpu speed controls in the BIOS and in Power Options I have set the cpu min and max to 100%.  CPU-Z shows the cpu as 3.4 Ghz.  I've disabled my wi-fi card and the onboard audio, turned off Windows sounds and all of the other tweaks that are recommended.  The tech told me to update the USB drivers, but the only available drivers for the motherboard are the chipset drivers, and I've already done that.  The USB 2 drivers shown in device manager are Microsoft drivers from 2006.  When I have device manager check for updated drivers, it says the best drivers are already installed.  Any advice?

Did you run latency monitor with Sonar running? I ran it with and without Sonar running. Without everything was good but with Sonar running I got the message my computer isn't capable of playing audio? The tech told me to update my BIOS but the company that built my computer highly advised against updating the BIOS. Better safe than sorry I'm just living with increase in my CPU usage. It's not a show stopper so at this point I'll just wait for Windows 10 and Focusrite to catch up with one another.