I have my reasons why I won't be upgrading to win10 any time soon.
a) because they are data mining you, that's why it's free. at least Facebook are upfront about it. MS have hidden it deep in the EULA.
b) I don't want Cortana, I hated it on Windows phone, and I don't want it on my desktop
c) It's another sloppy release from microsoft. Drivers that just 'sort of' work, devs that don't care and they laid off their entire test team and are now using early-adopters as guinea pigs.