I've had Windows 10 running on my main machine for a little over two weeks now, ever since it dropped in that weird staggered rollout at the end of July, and I think I've finally got it into a state where I don't want to throw the laptop out a window. So here's the stuff I actually changed, in case anyone else is still fighting with the defaults.
First thing: Wi-Fi Sense. If you haven't gone looking for this, go find it right now. Buried in Network & Internet settings, there's a feature that, by default, offers to share access to networks you connect to with your Outlook contacts, Skype contacts, and (if you've linked it) your Facebook friends. Not the password in plain text supposedly, it's some encrypted handshake thing, but the whole premise still made me uncomfortable. My home network got shared with god knows who the second I upgraded, because the setting was already on. I turned it off in Settings, and also did the thing where you rename your SSID to end in "_optout" — apparently Microsoft added that as an actual opt-out mechanism for networks you don't control, like if you're on someone else's router at a friend's place. I renamed our home network that way too, just to be safe, and yes my roommate was annoyed that all our devices had to reconnect.
Second: the privacy settings page in general is enormous, way bigger than it needed to be, and almost everything defaults to "on." Speech and typing data gets sent to Microsoft to improve Cortana and the keyboard, by default. Advertising ID is on by default, which is basically a persistent identifier tied to your Microsoft account so apps can target ads at you. Location is on. I went through every single toggle in there, one at a time, which took maybe fifteen minutes, and switched off everything I didn't have a specific reason to keep. I left location on because I actually use Cortana for weather and reminders, but I killed the ad ID and most of the "send data to Microsoft" stuff under feedback and diagnostics. Whether that actually stops much I honestly don't know, but it made me feel better.
The GWX icon deserves its own paragraph because it drove me up a wall for two straight weeks before I finally upgraded. That little Windows icon that sits in your system tray nagging you to reserve your free upgrade — it would not go away, it reappeared after reboots, and I read more than one account of people who clicked the wrong button and had the upgrade start scheduling itself on a machine they weren't ready to touch yet, like a work laptop. I get that Microsoft wants adoption numbers, they announced something like 14 million installs in the first 24 hours which is genuinely impressive, but the nagging felt more like a mobile game asking for a five-star review than an operating system update.
One actually useful tip, not a complaint: after you've upgraded and you're sure everything's stable, go into Disk Cleanup, click "Clean up system files," and there's a checkbox for "Previous Windows installations." Windows 10 keeps your entire old install around in a folder called windows.old in case you want to roll back, and on my machine that was eating something like 12 gigabytes. Once I was confident I wasn't going back to 8.1, I cleaned it out and got that space back immediately. Just don't do this on day one, give it a week or so of actual use first in case you hit something that makes you want to bail.
Start menu is back, obviously, that's the headline everyone already wrote about. It's fine. I've got it pinned down to a narrow single column because the live tiles thing never did anything for me, I don't need a weather tile pulsing at me while I'm trying to open Notepad. Edge is also fine, faster than IE ever was, though I still keep Chrome around because half my bookmarks and extensions live there and I'm not about to redo all of that on a whim.
Anyway. If you're two weeks out and still poking at settings like I was, that's basically the checklist: Wi-Fi Sense off, privacy toggles gone through one by one, windows.old cleared once you're confident, and just accept that the GWX icon is going to sit there mocking you until you either upgrade or find the registry hack to kill it.