For the guys who are facing issue in Windows 10 after upgrading from Windows 7/8, I have experienced the same as well. Not as severe as mentioned here but there were issues and incompatibility with some applications. However after a while when 1511 released I decided to make a clean windows 10 install. So I have used a vcs script to get my product key, downloaded the iso from internet and tried to make a fresh install.
Now when I have provided the key during installation it was not working and I panicked that I need to reinstalled Windows 7 and upgrade to Window 10. But a little bit of googling helped me to know that Microsoft stores your hardware signature and will activate your copy automatically.
After that first activation is complete, you can perform a clean install on that same hardware using an ISO file, which has a product key embedded in it. As long as the hardware matches the previous installation ID, the installation is activated automatically. (Microsoft does not provide details of what goes into the hardware ID, except to confirm that it does not contain any personally identifiable information and is not used for tracking purposes.)
Source: Windows 10: You've got questions, I've got answers
So I have installed Windows 10 without product key. And after installation it was activated automatically. Now my system it much better, smooth and almost with no issues. Al my applications are working fine and I am quite satisfied. So I guess a clean installation will help to iron out a lot of issues we all are facing. And in my opinion it is worth the upgrade.
Also my dad have a laptop that came with Windows 10 Home pre installed and it is working quite fine. He is not an enthusiast user like me but for all his works (drafting, banking, office works, movies, games) it is fine.
P.S. I have Windows 10 Pro