Alrighty, installed on my SP3 just fine, Win8.1 > 10074 > 10030. Doing it's initial install stuff, updating 108GB of OneDrive, etc. I'll let it work overnight before using it, so I get the best idea of it's actual performance. Seems solid enough as I poke around with it, however.
Also installed on my desktop, where it's now officially my favorite OS--ever. It needs some spit and polish, but performance is excellent and features are spot-on. It's a great combination of what was best about Win8.1 and Win7. A phenomenal job on the part of the Windows team.
The install on my Dell Venue 8 Pro is going very slowly, but it's progressing. Can't wait to see how it runs there--if it works on that little guy, it'll hit all the buttons for me.