I haven't. I have friends that have, and those that upgraded
generally love it. I'm not crazy about the permanent always-on
connection to the Internet that's sorta necessary, nor the
scrambling of the hard drive for encryption (after my mother's
computer got hit by CryptoWall 2.0 ransom, I'm really not keen
on that idea being used.
That being said, if my next computer COMES WITH Win10, I'll keep
it. I'd just go with the flow at that point.