In addition to what others have said, privacy is a big issue as well. Of course, other versions of windows have probably been sending all your info to MS but WIndows 10 is the most brazen about it. By default pretty much
everything you do is recorded, logged, and sent to MS, including keystrokes and even voice recordings (if you have Cortana enabled). You have to wade through several screens to turn all that crap off, and there have been a couple occasions where I've noticed that after an update some of the settings were set to
on again. Oh, and btw, a couple of the settings can
only be switched off from an external website. And that's assuming the settings actually work as intended, there's some evidence suggesting that Windows 10 is sending some of the data anyways.
Also by default Windows 10 uses your internet connection to download copies of WIndows 10 onto other computers. Ya.
The user agreement has some... interesting features. Take privacy for example:
"We will access, disclose and preserve personal data, including your content (such as the content of your emails, other private communications or files in private folders), when we have a good faith belief that doing so is necessary to protect our customers or enforce the terms governing the use of the services."
Do you want to rely on Microsoft's "good faith"? I don't think previous versions of Windows had a catch-all like that.
Or how about intellectual property rights?
"When you share Your Content with other people, you expressly agree that anyone you’ve shared Your Content with may, for free and worldwide, use, save, record, reproduce, transmit, display, communicate … Your Content. If you do not want others to have that ability, do not use the Services to share Your Content.”
“you grant Microsoft a worldwide and royalty free intellectual property licence to use Your Content, for example, to make copies of, retain, transmit, reformat, distribute via communication tools and display Your Content on the Services. If you publish Your Content in areas of the Service where it is rendered available online publicly or without restrictions, Your Content may appear in demonstrations or materials that promote the Service.”
Again, not sure about the agreement in previous versions of Windows, though I haven't found anything yet to suggest they are as extensive as that.
Based on the user agreement I've been advised not to use Windows 10 as I would be at serious risk of breaching client privilege.
And let's talk about the updates. In Windows 10 all updates and upgrades are mandatory, and if you're stuck with 10 Home they are downloaded and installed the moment they become available. Updates in 10 Pro are also downloaded and installed immediately, though you can "defer" an upgrade for an unspecified amount of time. Don't want to be a guinea pig? Too bad. Have software / hardware that suddenly becomes unusable due to an update? Too bad - if you roll back the update which caused the problem, Win 10 will apparently keep downloading and installing the update over and over again. Don't want new features which bloat your computer / slow it down / spy on you? Too bad - again,
everything is mandatory, whether you like it or not.
For most users I doubt this matters much, but I'm not a fan of it.
Isn't the update generally just 10 Home? Or do you get updated to whatever matches your current version of Windows, like if you have 8 Pro you get 10 Pro or whatever?
You get upgraded to whatever version matches your current version. From what I can tell, the main differences between 10 Home and 10 Pro is that 10 Pro does not have ads by default (it's pretty pathetic that's now considered a selling point) and that you can defer major upgrades (though not updates) for an unspecified amount of time. You're still forced to have the major upgrades, but only after all the 10 Home
losers users have kindly worked out some of the bugs for you. Won't help much if its bloatware though.