I'm just afraid, that when Windows 10 installs as an upgrade, the result will be similar as to when one Beta Test version installs as an upgrade to a previous version. Some things will change.
Every time I've installed a Beta version over a previous Beta version, two things have happened that I had to repair.
I can do the repairs, but a casual user will not know how to do that, and there will be a lot of very unhappy users out there.

For one, if a person is using System Restore, that feature will be shut off and all old restore points will be deleted.
I use Windows Mail, re-activated, as my email program, but I have to re-activate it every time I do an upgrade.

I'm pretty sure that there will be other programs that will stop working as a result of the upgrade.
Computer tech's should make a fortune off of this one. Thank you Microsoft!

I've already sent an email to all my Computer customers, to beware of the Windows 10 upgrade.

Cheers Mates!