Win 10 is coming like it or not
You can stop the auto upgrade, details below....
I speak as an IT Tech for a well known UK University & have been involved in trialling it from an Enterprise Business user point of view. I've been running various builds, inc the release version for about a year, on various old & new pc's.
But we can build our own custom .WIM's for our own use, and always do fresh 100% new installs.
Plusses: Stable, better memory management, error handling better, all round a good thing. Learning curve is way less than Win8.x
Negatives: It can (& does) install itself as an 'ahem' update from MS update (!)
It can trash working systems (!) a very small %age, but that no consolation if it's your production pc. (it keeps trying to apply a patch that breaks it, then rolls it back, & applies the patch again!)
It can be rolled back for free for 30 days, but that in itself can trash your pc, but buy external storage/drive/memory stick & back up your data first, but hay, we do that anyway, don't we?
TO GET RID OF THE UPDATE NAG: (on Win7 pc's)
go to:
Control Panel\All Control Panel Items\Programs and Features\Installed Updates
search for KB3035583 & Uninstall it.
Above info: act at your own risk/your milage may vary/close cover before striking/seek indepenent medical advice/ & don't sue, I'm divorced (the x & her lawyers got everything!)
I don't like the way it appears to collect a lot of personal data/spying on you/dial level of personal discomfort here... although it appears to be for advertising purposes.
There are articles on what & how it does on 'T'Internet, as here UK's Independent Newspaper
good luck