I'm gonna stick with 7 for the mo, but I'm downloading the win 10 ISO from MS for installation later (and after everyone else has suffered their installs, so I can make an informed choice - or something like that).
Actually I might just whip out all my SSD's / HDD's and chuck some new one's in (they're cheapish enough these days), chuck 7 with sp1 on, then fire 10 at my machine...
or I might just go down the pub and not worry about it?
Anyway, link to the MS Media Creation Tool for win 10 if ya wants it (you know you do).
Happy PC murdering
Edit:
Looks like you can do a clean install of 10 if you create a bootable DVD from the ISO (so no need to install 7 or 8.1 first)