Doing a little research has uncovered the following:
Plus updates are always "Automatic" - you can't control when you get 'em or what you get. The former is a no go for me since I'm often on flaky/slow internet connections and need to be careful about what goes on behind the scenes when I'm online trying to send an email or read my email. The latter can result in driver conflicts - not all drivers download via Microsoft Update are the correct ones - see the article above.
So can you live with all of the above - and anything else it does weird that is not yet discovered?
If you have Win/7,
WAIT! Check back here and see what I'm saying in January, 2016. DON'T UPGRADE! Read this: Windows 10 is a better Windows 7 if you can get the upgrade to work. Given the problems encountered by the author of that article, plus all the stuff above, I recommend against attempting an upgrade to Win/10 from Win/7.
I have no plans to ever upgrade my current Win/7 system to Win/10.
If you have Win/8 or Win/8.1: MAYBE! Win/10 does seem to be a better OS than Win/8.x. But there are still all the privacy concerns. And given that it is possible to circumvent some of the privacy attacks in Win/8.x (see below), you just might want to stay with your Win8.x system.
If you are buying a new computer, well you might be stuck with Win/10. Be sure to read all the above links (and more below) to figure out how to stop the most egregious privacy problems.
When Microsoft announced Win/10 and the free upgrade, I was pleased and had every intention of upgrading a few months after it was released. Now that I see how insecure Win/10 is, I will never use it as my main system (unless these privacy issues are resolved). I figure I'll be switching to Linux when I buy my next computer and running Wine on a dual boot system, using the Win/10 side only when absolutely necessary.
Microsoft slips user-tracking tools into Windows 7, 8 amidst Windows 10 privacy storm - PCWorld. Now it appears you have to modify your Win/7 or Win/8 system if you want privacy. The article tells how. Creepy! Good Luck.
P.S. I have now uninstalled the updates as the article describes with no problems.
It just keeps on getting worse - there are more updates that need to be uninstalled as well as other measures to take. See Stop Windows Telemetry/Tracking/Upgrading to Win10 « alaya:techne.
Dual-booting Linux with Windows: What you need to know | PCWorld
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How To Stop Windows 10's Spying Ads | Rock, Paper, Shotgun
Classic Shell and Start10 banish Windows 10 Live Tiles, bring back Windows 7 look | PCWorld
How to reclaim your privacy in Windows 10, piece by piece | PCWorld
How to cure Windows 10's worst headaches | PCWorld
How to turn on System Restore in Windows 10 to protect against bad updates | PCWorld
How to change Windows 10's default web browser to Chrome, Firefox, or Opera | PCWorld
How to change Windows 10's default apps | PCWorld
How to customize Windows 10's Start Menu | PCWorld
How to customize the left side of the Windows 10 Start menu | PCWorld
How to disable Windows 10 File Explorer's new Quick Access view | PCWorld
How to stop Windows 10 from using your PC's bandwidth to update strangers' systems | PCWorld
How to stop Windows 10's annoying Microsoft Office ads | PCWorld
How to stop Windows 10 from pestering you with ads
How to turn off Windows 10's keylogger (yes, it still has one) | PCWorld
If you installed Windows 10 and like privacy, you checked the defaults, right? Oh dear - The Register
The Windows 10 Security Settings You Need to Know | WIRED
Windows 10 doesn't offer much privacy by default: Here's how to fix it | Ars Technica
Windows 10 is spying on almost everything you do - here's how to opt out | BGR
Windows 10 Upgrade: First 5 things to do after Windows 10 download | BGR
Windows 10: How to choose default apps - Liliputing
Windows 10's default privacy settings and controls leave much to be desired | ExtremeTech
Windows 10 Security Settings You Need to Know | WIRED
Windows 10: The best hidden features, tips, and tricks | ExtremeTech
How to Disable Windows 10 Data Collection
Did you upgrade to Windows 10 and now regret it? You can go back to your older operating system in a few clicks: How to uninstall Windows 10 and go back to Windows 7 or 8
If you are staying with Win/7 or Win/8: