This is the official documentation: Windows10-upgrade-instructions.pdf
Speaking from personal experience, I got an ICS that someone returned to Amazon, clearly unable to get the Win 10 upgrade to work (Wouldn't boot). I upgraded the BIOS and did a complete system restore. Went through the process to setup Win 8 (Username, password, colors, etc). I then downloaded the Media Creation Tool from Microsoft to the ICS and created a bootable thumb drive using the tool (I imagine an SD card would work just as well). After waiting for the download and creation of the bootable thumb drive (This takes some time) I ran the setup while in Windows 8.1 from the thumb drive and selected ... the second option ... Not to upgrade but to do a fresh install over the existing Win 8 partition and download all of the updates before installing.
This is my personal experience, YMMV. I did all of this earlier this week.
I had no issues with my Surface Pro 2, or any I have noticed.
I have installed using the ISO image I had downloaded prior to the 10586 release, version 10240 and it's working fine again. But the issue I'm worried about is that Microsoft no longer give users direct access to choose what updates are install. It's an all or nothing deal. There was an option to ignore new builds which I selected (can't find it again), that I'm hoping will ensure it doesn't decide to update on it's own and 'brick' my current device.
VyReN it appears you might be a little confused with my question. My issue is with the 1511 10586 release. But if John-B is correct, Microsoft might have pulled it. Shame it might have results in a lot of non-functional systems for people.
Thank you for joining the Intel communities.
Microsoft has posted the improvement for Windows 10 version 1511.
Please be aware that for you to upgrade to Windows 10 you will need a BIOS version 0024 or later in your system, if you have a version older than that you will need to update the BIOS in order to do the upgrade.
Also, you can see my post here: