it works good.
I ran 14/46 gearing, and it wasn't as fast as with the 1512 2.5d, but it had a little more torque, but it's hard to judge, because I also used the 50k center diff fluid w/ the 1515, so it wheelies fairly easily now.
but, temps were VERY good. the batteries got warm, not much over ambient though, the motor was just a little warmer, and the quark/heatsink were only as warm as the batteries. it was only a 7 minute run, but when I used the 1512, the motor and controller would got this warm idleing lol (not really, but it got very hot, very quickly).

finally the motor moved a little, and stripped the diff gear. 3rd time this has happened.. more threadlock on the motor screws?

speeds are I'm only guessing, but 35ish? going up on pinion a bit will get my speed back :)
I'll post a video later tonight.