I upgraded on my Lenovo W540 and built a new VM that I use on my desktop here at home (for work things). So far a few minor glitches here and there, but generally solid. Start menu is way better than the train-wreck forced metro thing they kept trying to ram down our throats.
Cortana is a MASSIVE battery hog, not to mention all the various privacy concerns, so I shut her down (and locked down the system to some degree... though... really... they're still watching and I know it.)
Doom and gloom remarks aside, Microsoft has this pretty well down. The code base for the Windows OS has not changed nearly as much as it used to in the olden days. The core of NT and all it's relative goodness is still buried in there (along with Win2K, XP, Vista (eek), Win7, etc.)
The upgrades I've seen so far have been VERY smooth, though once upgraded I did blow my system away to get a fresh install because I prefer it that way.
I think you're safe to move with it, but I do recommend looking into some of the privacy concerns and shutting some things down pretty quick.