David Auerbach's got a good piece on Slate about Windows 10's crappy default privacy settings and how to fix them
. I'd figured out about half of them on my own (the obvious ones; not tying your login to an MS account and disabling the Start menu's internet search "feature") but the other half were a lot less discoverable.
tl;dr you're going to want to go to Settings -> Privacy Settings and click through each and every single menu there to see what all Microsoft is sharing and disable the stuff you'd rather they not share.
And while I've stated in the past that I think MS's automatic LAN sharing of updates is a great idea, what I didn't know was that by default it's Internet
sharing of updates, which is almost certainly something you don't want. (My immediate reaction to this was "Oh, so THAT'S why my Internet connection has sucked for the past month," but that's probably unrelated; while there have been a few times I've experienced slowdown, checked my bandwidth, and seen a mystery upload, most of the time when my connection is bad I don't see anything getting in or out. So it's probably the usual "Cox is terrible (but still maybe the least terrible ISP)" reason.)
There's a lot to like about Windows 10, but usual "wait for the service pack" cautions apply. You've got a year to get your free upgrade; if you don't have a reason to rush, then the first rule of Tautology Club. If you do upgrade, though, you should probably read that article.