Bit the bullet and installed windows 10 insider preview. In spite of or because of how old my box is (2007) everything except the WiFi dongle was recognized. Latest Build as of this post (100130) has Intel drivers that make gaming and video about as good as it was before with vista. This translates to pre-2005 games and decent YouTube speeds.
This isn't a big feature by feature run down since just about anywhere will have a breakdown of all the shinies. This is just my experiences so far. Put bluntly, so far I like it. There are a few minor hiccups, but on the whole it works surprisingly well on even old hardware. Granted it's a dual core with three gigs of ram, but daily browsing and the like via Edge (Formerly Spartan, and basically a rebranded Internet Explorer) is pretty alright.
Cortana, live tiles, not even the return of the start menu matters to me. What matters is I'm not left wondering where everything is. I cannot stress that enough. Beating my head against the wall trying to figure out where what is was what made doing anything in 8 and even 8.1 a headache and I am glad Microsoft realized their mistake after everyone on the internet screamed at them for a few years.
All the integration with bing, OneDrive, windows store. Eh. Cortana can be made deaf, you can install your own browser, the store is completely a non-issue for x86, and the live tile thing is essentially the pinned programs section of the start menu in older versions, except metro apps can be made to show information without clicking on them.
There are a few negatives though. Biggest one so far is that windows wouldn't recognize my tablet's SD card when I/stuck it in my computer's reader (vista did.) Thankfully it was recognized when I plugged the tablet in, but that is an issue that could scare people. Additionally while I could find everything more or less OK and search helped me with what I couldn't there was a little bit of a hangup when trying to find windows update since I'm used to it being in the control panel. Nope, it's in settings. Just type windows update into search and it'll be there.
Lastly I am mildly concerned the insider preview has a shelf life. 7 and 8 get free upgrades. Why not unlock the insider preview to a full version like they're getting instead of having it become unusable in October? Maybe they'll do that, I dunno.