My own experience and that of riding buddies with Rotor gear is very positive. I run a Rotor oval chainring on my XTR M9000 11-speed crank, and the experience is flawless. Rotor was thoughtful enough to include four beautifully machined end pieces (the bits the charinring bolts screw into), which are much, much easier to fit than Shimano’s (which are not identical even though they look identical and constantly want to turn and thus, misalign, when you fasten the bolts).
The craftsmanship is excellent, easily DuraAce/XTR/Red/XX1 level. The modular design is really cool, too. I might go for a Rotor crank on my next bike, I really like running their oval rings on my mountain bike.