I'd finally got some lipo's (TrueRc 8000mah packs, a 3s2p and a 2s2p used in series) and I tried them in my e-maxx with a neu 1515 2.5d.
Gearing is 51/20 (20t pinion is the only gearing option I have at the moment, because the motor hits the transmission with smaller pinions and I don't have an 18t or a bigger spur yet). It's using stock diff gears and is locked in 2nd (12.499:1 final drive ratio).
After this run the motor was 32 degrees C (90f) and crept up to 35C (95f) after sitting for a minute then went back down. The Quark 125 wasn't really any warmer than the motor (I don't think that means much though since I haven't done the internal heat sink mod). The batteries were barely warm. I had used it for a few minutes about 5 minutes before this vid though.
So far I'm happy with these batteries and motor, but I'm not a huge fan of the quark (this is my 3rd one). Yes it does cog a bit at the start.
The video is 2 minutes 20 and sorry the quality isn't that good.
http://www.youtube.com/watch?v=ZMZeTJFA2f4