My experience of transferring Win 8.1 retail license to another machine was terrible. MS made it so difficult and unfriendly.
I have a question right now:
If I upgraded to Windows 10 from my retail licensed Windows 8.1 Machine. Can I then freely transfer to another machine and stay as retailed licensee?
If you "roll your own" PC there is an amazing choice available to you. Windows is no longer the resource hog it was 8 or so years ago, and since Windows 7, there has been a slimming down of features and an increase in performance for Windows systems, as well as excellent stability and security. My specs show a modestly specified ten year old machine, and it has no problems with performance - of course I don't play games or do video editing, but normal use it is fine with.
With a well spec'd new system and an SSD for fast boots, 10 will fly.
I have to say that I have no experience with transferring retail Windows Licenses. I guess that confidence will count for a lot, and not losing your rag when some agent is uncooperative. I do Intend to transfer a retail channel Windows 8.1 license, soon, and it is my right to do so under the terms of the license I have, so I don't anticipate problems.
Windows 10 upgrade will inherit the retail characteristics of the system upgraded from definitely.
Hopefully. We'll see... how MS will proceed this. Maybe I will get a another Windows 10 retail license.