Having had Windows 10 for 48hours now on my number 2 laptop and painlessly – and very quickly - updated my main computer to it this morning I can see no real advantage or disadvantage to it over W7 or W8.1 . . . . . . . for 99% of the time I don’t see the operating system when I using a computer – it is just there to run and present programs . . .
I share this ^^^ opinion; as stated above, I don't see the operating system when I use a computer, so I'm going to stay with Windows 7 Pro.
We've got 11 more months to redeem the free upgrade offer. I'm going to wait for more bugs to be worked out {just like any other new OS} and wait for the opinions of both the general public and tech critics to be built up by months of use. Win 10's current offerings don't jive with me. Maybe after some updates, I'll change my mind.
Upgrading the OS isn't going to be some magic super boost. Upgrading and then deciding to downgrade wastes your time and also has a chance of screwing up your system, programs, and settings in ways you might not notice for months. So if/when you do upgrade, be sure to make a full system backup on an external drive (wouldn't even trust internal with the way the Windows installer has handled things in the past).
I'm concerned about privacy issues, as outlined here :
http://i.imgur.com/9DoVoix.jpg