If Microsoft would reverse course on their new forced updates and privacy policies, I'd be singing Windows 10's praises more. I've had no real issues with 10 since installing it on my laptop the day after it was released (I'm keeping 7 on my desktop, though). It's the update Windows 8 should have been, and it's been a very efficient OS so far.
The problem is, a year or two from now it could be an entirely different OS, or an update could break something critical in your workflow, and you just have to deal with it.
I'm surprised they're going in the direction they are so aggressively with privacy and forced updates, given all the commendable charitable work Bill Gates does via his foundation (naive of me, perhaps). If they don't make some changes to their new policies, I think they could face some big legal battles down the road.