If if works in W8.1 it will work in W10.  Not too long ago I found a vendor who sold Windows Anytime Upgrade from W7 Home to Pro.   They turned out to be OEM licenses which can be a hassle upgrading hardware. MS is no longer doing OEM licenses so I'm upgrading all systems to W10.  It is a nice OS.

I've been using it for a while without issue...my Focusrite Forte works
without issue...and ALL my DAW's and programs are fine with it....
I upgraded from Win 8.1....

I have the tech preview and everything works so far.

JClosed
@kevinwal
 
Well - problem is, that from Windows 8 the legacy support (drivers) of FireWire is removed. This has to be installed separately (Microsoft provided that drivers for download after complaints), but sadly this will not work with the older Saffire drivers. The legacy drivers used in Windows 7 worked great, but those installed in Windows 8 (and higher) just do not work. I tried it several times, but it was an no-go.
 
So- while FireWire is supported in Windows 8/10 there are differences that can have impact on some older hardware (mind you - I do not say every hardware). MOTU has good supported drivers. I wish I would have spend an little more an few years back to get that hardware, but well.. Budget is not always that great...
 
Glad it is working for you tough..

You can download the legacy FireWire drivers from MS. However if you are using the latest mix control Focusrite DO NOT recommend the legacy FireWire drivers (like they have done with previous versions).

If you have issues with latest drivers. Full uninstall mixcontrol, reboot, install latest. Reset settings within mix control everywhere. Once it's configured save it to hardware.

Saffire Pro 40 and Win 8.1 work great for me.

FYI from BOSS.  I have some of their gear ...
 
http://www.boss.info/support/support_news/250011
 

About BOSS product support for Windows(R) 10

Thank you sincerely for your ongoing use of products from BOSS.
Our statement regarding the use of BOSS products in combination with Microsoft Windows 10 is as follows.
At present, the drivers compatible with Microsoft(R) Windows(R) 8/8.1 that are available from BOSS's website do not support Windows 10.
With respect to Windows 10 compatibility information for BOSS products and driver support, we will proceed with verification following the release of the official version of Windows 10. We ask for your patience for the while until the information becomes available. We plan to announce the status of Windows 10 compatibility for BOSS products that are compatible with Windows 8.1.

So they didn't work with Microsoft? They are waiting until release to start working on a driver? Way to be proactive!

The Win 8.1 drivers for my Roland Studio-Capture work on Win 10.  The Vista drivers for my Frontier Tranzport work in Win 10 (but they must be installed in compatibility mode, the same as I had to do for Win 8.1).  My BCF2000 worked with Windows plug and play drivers.
 
Unless there is some specific item, in most cases if it works on Win 8.1 it will work in Win 10.

They have a nasty habit of owning the "won't work in another OS" version. All some do is ask for a specific version and if it ain't there, they won't install. It has little to do with whether or not the driver itself is compatible. Not a good model of efficiency...

fireberd
The Win 8.1 drivers for my Roland Studio-Capture work on Win 10.  The Vista drivers for my Frontier Tranzport work in Win 10 (but they must be installed in compatibility mode, the same as I had to do for Win 8.1).  My BCF2000 worked with Windows plug and play drivers.
 
Unless there is some specific item, in most cases if it works on Win 8.1 it will work in Win 10.

It's prolly Roland's way of avoiding a support headaches until they get thru quals on 10.

Doktor Avalanche

JClosed
@kevinwal
 
Well - problem is, that from Windows 8 the legacy support (drivers) of FireWire is removed. This has to be installed separately (Microsoft provided that drivers for download after complaints), but sadly this will not work with the older Saffire drivers. The legacy drivers used in Windows 7 worked great, but those installed in Windows 8 (and higher) just do not work. I tried it several times, but it was an no-go.
 
So- while FireWire is supported in Windows 8/10 there are differences that can have impact on some older hardware (mind you - I do not say every hardware). MOTU has good supported drivers. I wish I would have spend an little more an few years back to get that hardware, but well.. Budget is not always that great...
 
Glad it is working for you tough..

You can download the legacy FireWire drivers from MS. However if you are using the latest mix control Focusrite DO NOT recommend the legacy FireWire drivers (like they have done with previous versions).

If you have issues with latest drivers. Full uninstall mixcontrol, reboot, install latest. Reset settings within mix control everywhere. Once it's configured save it to hardware.

Saffire Pro 40 and Win 8.1 work great for me.

I do not doubt that, but -as I said- I have an Saffire (the white/silver model), and that latest mixcontrol does not support that older hardware. So I have to use the outdated mixcontrol and the legacy drivers. As I have no budget at this moment to buy newer hardware with the same capability's as my present hardware, upgrading to Windows 10 for me is an no-go.
 
It is no Windows problem (although it is an bit strange the Windows 8 legacy drivers seem to work different than the Windows 7 legacy drivers) . It is Focusrite that does not want to support older hardware on newer windows..