Ok - good news here, at least with a preliminary test.  I got the PCR-800 working connected to my Surface Pro 3.
Before, when I'd plug in the USB cable, the display would come on, stay lit for about 5-10 seconds, go dim, then turn off.  Install would not proceed to see the device plugged in, and then could not do anything with it because it wouldn't even power on.
 
So I used the above-linked advice and it's all seemingly working.
Now I have the driver installed successfully, and when running a cheap free midi sequencer I found (not installing Sonar on the Surface), it recorded and played back the recorded midi.  I can only make assumptions about anything more than that, but I'm guessing it's good to go.
 
So, here is what I had to do to make it work: (disclaimer: do at your own risk - might not work, might blow up your system, could prevent you from making a living, might even turn your tongue green for all I know)...
 
Download and extract the drivers from the Rolnd site - I used the 8.0/8.1 set for the PCR-800
Go to the \files\64bit\files\rdif1027.inf file and edit it (assuming 64 bit - I imagine the 32 would be the same process)
At the [Manufacturer] line, change the next line to read:
%MfgName%=Roland,NTamd64.6.2,NTamd64.10
 
At the [Roland.NTamd64.6.2] - change this to read:
[Roland.NTamd64.10]
 
Save this file
 
Now, go to Start and type Change Advanced startup options and run that selection
Under the Advanced Startup section, click Restart Now
When you get the "Choose an Option" Screen, select Troiubleshoot, then Advanced Options, then Startup Settings
Click Restart
You will get a menu of items to choose from - select the option "Disable driver signature enforcement"
 
Now, in my case, I went back to the INF file, right clicked it and chose install.  It didn't work first time for me because I hadn't made one of those text file edits, but after I did, I went to the Device Manager, saw the PCR device in Other devices with a (!), so I selected Update Driver, browsed back to the INF folder and I was presented with the "Do you really want to install this driver" screen, to which I said yes.
 
Driver was then successfully installed.
 
Now - to get the guts to do this to my music PC!  Not tonight, but maybe this weekend.  I will update back here with my success or failure :)
 
Thanks for any help from the folks who have provided it - especially that last one from MackTheKnight

I took the plunge and Wednesday evening (29th) upgraded my Win 8.1 Pro x64 DAW OS to Win 10 Pro x64. Overall it went well, I had to spend many hours tracking down why my LAN no longer worked. I needed to re-install drivers for a number of my DAW accessories (Frontier TranzPort, Roland UM-1S Midi Interface) which no longer worked after the upgrade. But, I am confident that as far as my installed apps/devices, I am now in at least as good a place, as I was with v8.1. Even my iLok 2 went through the upgrade unscathed, as my iLok protected plug-ins still work as before. It seems I am able to play back projects at a notch lower ASIO buffer size latency without crackling in the audio. My Apollo QUAD, (2) UAD-2 PCIe cards and UAD plug-ins are working fine with no errors or driver issues. As I was checking out the Win 10 TB settings, I saw an entry for a Thunderbolt Certified Device for PC and I nearly fell on the floor! So I plugged my Apollo Twin directly into one of my two TB 2.0 ports on my PC DAW MB and also daisy chained off of my Apollo Quad TB card and both times when I turned my Twin on it was recognized as a Win Certified TB device and was successfully connected for use. Not expecting that it would, I did check to see if it would work with my existing Apollo Console 1.0. No go of course, being that the Apollo Twin never ran on the PC before (no software/driver support) and needs "PCIe" audio drivers (like on Mac) to work I was not expecting it to. But, it seems we are real close to getting the Apollo's running under TB on PC's. I think the next milestone will be when UA releases the Apollo Console 2.0 PC update, PCIe audio drivers and MS "officially" updates Win 10 for TB support. The ground work has been set and I am expecting this all to culminate in the months ahead. Woohoo!
 

 
This is nothing scientific mind you, but I 've noticed projects in Splat that would playback fine @ 64 ASIO samples, but crackle @ 32 samples using Win 8.1 are now crackle free @ 32 samples using Win 10. I noticed the same thing in REAPER. It seems whatever under the hood audio improvements MS did to Win 10 has made a tangible low latency difference. It is like I can get a notch lower buffer setting crackle free now. I would never be able to play a project (many audio tracks/plug-ins) crackle free in Splat @ 32 samples using my Apollo Quad's FW audio drivers. But amazingly, now I can! I can only imagine how much better the low latency performance will be once UA releases actual PCIe audio drivers for Win 10 & TB.

I am glad I made the upgrade. Kudos to Cake for being the first major developer to offer a certified & supported Win 10 compatible DAW too! Win 10 seems snappier with noticeable improved latency performance. In addition, I am all set to jump on the certified and supported Win 10 Thunderbolt goodness when it "officially" arrives in the months ahead. From the looks of it, Apollo TB support is already in the pipeline and MS Win 10 approved and certified!

Cheers,

Billy Buck
 

In the vein of what Billy Buck is reporting - performance improvements.  This is not related to Sonar, but an indicator of more under-the-hood stuff.  On my Surface Pro 3, the WiFi drivers have always been a problem.  It's a pretty well-known fact that the Wifi on these is slower than it should be, specifically when using certain routers in certain modes.  For me, that was a 802.11g router at 2.4ghz.  The best I could ever get on this machine was about 17mbps when I have 100mbps Comcast service, that tests as such on the wired side.  I didn't have the extra cash around to spring for a new wireless router with dual-band and really didn't need it for what I do most on this laptop when here at the house.
 
I had a spare router at the office that was newer and suppose 802.11n, but still only at 2.4ghz.  Since the issues that have been reported have more to do with 2.4 vs 5, I didn't expect much, but I brought it home last week and got connected.  Under Win8.1, my speeds went from the terrible 15mbps to around 45mbps.  This is a huge improvement, and a noticeable one.
 
Fast forward to a few days ago - I've updated the Surface Pro 3 to Windows 10.  Same router, same test, now I'm consistently getting about 80mbps.  I'd say something changed, wouldn't you?
 
For all the MS haters out there, being an MCSE, and an IT professional running my own support business, I hear complaints all day every day about this or that, how bad Windows 8 was, etc.  So far, my own experiences and those I've heard out in the field have been almost all good.  For once, maybe MS got this thing right :)