I've heard you can activate Windows 10 with a key from 7 or 8.1 [1].

[1] https://arstechnica.com/information-technology/2017/05/windo...

Does it provide a trimmed down version of the upgrade? Will I be able to use Ubuntu subsystem?

As graton alludes to with his upgrade link, the trick is to get to the upgrade through an accessibility link. Windows 10 is still free for people that require accessibility services (presumably since it has better accessibility features), but there's no actual requirement behind that.

You can still activate W10 using 7/8 keys and most of the other methods still work. At least that's what people say on /r/windows10.

I really like most of windows 10. My main complaint is the start menu, I have yet to figure out how I'm supposed to use it

I use it the same way I use Spotlight on mac and gnome-do on Ubuntu. I press a key-combo and it gives me a prompt to start typing a few characters that'll probably take me to what I'm looking for.

I can't stand the Windows 10 Start Menu. I paid 5 bucks for Start10 [1], although some people like the free Classic Shell [2].

[1] http://www.stardock.com/products/start10/ [2] http://www.classicshell.net/

To me it seems like you're mostly supposed to use Cortana search. They've taken the same approach as macOS and Ubuntu it seems.

I unpinned everything, and just operate it entirely by keyboard: hit the windows key, type the first few characters of the program name, hit enter. I find I don't even need to look at it most of the time.

you're supposed to pin your most used apps as tiles

I downloaded the iso during the free upgrade period but didn't get around to installing it until last weekend.

On my first attempt I agreed to a prompt to download updates to the installer; it then told me I needed to have a key to continue.

So I started again without downloading the updates, and I could install and activate without a key.