Can you quantify that? 10 degrees? Over how long?

yeah.
Please offer us detailed information about the temperature difference and running parameters.
I doubt the necessary of the "new design".Cogging is rarely a problem in my original 1515/1Y.
The Novak improves their motor performance by increasing the magnetic field of the rotor and hence more difficult shaft rotation.
Maybe the Neu goes to totally different way but that completely overthrows my concept from Novak.

Yes, do tell. This is very valuable information. I can't believe they would sacrifice efficiency... if it is the case that they run hotter, i wish they would have left it alone, or at the very least, IMPROVE efficiency.

I find this odd though, theoretically, a slotless motor should be more efficient, and more power dense, but from what products are available, this is not the case. I wonder what would come if Neu made a good slotless design, targeted around efficiency (I've seen slotless designs hit 98+%), but obviously, power density would be reduced, but then again, we don't even use these motors to their full potential, so it might just end up being a winner. Most ppl only push their motor to roughly 60% peak power.

I never had problems with my original Neu 1515/1.5d cogging.