It was my understanding that Pirated copies will still be labeled as pirated even after a upgrade. Not sure how this will work or what the implications are though.

Windows 10 has worked quite well for me. no major issues over the last few builds. Spartan is pretty good as well, but it still has some issues to be worked out.

I feel there could be more customization options for the start menu. While its much better than 8 I feel people are going to still be installing Classic Shell to get something they can customize a bit more.

Its seems to be less memory intensive that windows 7, but that could just be the lake of services I have running. I do notice the built in Anti-Malware software can get high CPU usage for a extended period of time. I just added it to my Daughters ancient laptop with only 2G Ram and its been working great so far.

I will probably dual boot for sometime to make sure there are no major issues at launch, but it looks to be a vast improvement over windows 8.