I had an i7 ASUS Republic of Gamer's laptop with Win 8.1 - decided to install Win 10 (I don't perform upgrades anymore)
I download the windows 10 ISO and burned to DVD. Booted from the DVD and performed a clean install (no reformat kept all my data and old windows files incase I needed to roll back)
So far system operates much faster, however booting up and shutting down are slower.
It is a stable install with no issue in installing programs, streaming, and heavy internet traffic - I forced a 100GB download at 12 MB/S and recorded sustained activity without interuptions, so basically the internet operation within the OS will run at the maximum speed of your internet link, or your hardware. I forced a 1 TB wireless multi-file transfer @ 300 MB/s and it ran flawlessly as well - so wireless local network operations score very well. Wired transfers run at Gigabit speeds.
Had a glitch in installing the latest Nvidia video card drivers - took 3 attempts to get them to remain installed.
Installed VMWare and started my old windows 7 box and played out dated games, ran outdated programs, and browsed outdated files within the Virtualized windows 7 Pro system without issue.
Performed the same for old Vista system that I virtualized as a test box, runs without issues.
All in All - if you can do a clean install - I say go for it... Win 10 will be good to go...
If you MUST have you old Win 7/Vista/ ETC... systems - I say install Win 10, and VMware cleanly, Perform a VM Convertion on your old systems, making them virtual, and run the Win 7 virtually on Win 10 - This is one way to never lose any of your old systems - they will be preserved to the data that you converted them to VM...
If you have upgraded to a new system with more RAM and CPU - then you will get the benefit of running you VM server on that new more powerful system...
Best of all VMWare Player, and VMWare converter are free tools offered from VmWare.