I just acquired some Apogee 3S 3800mah packs. So far, they've been pretty impressive.
The Limn chemistry doesn't hold the voltage under a load that the Turnigy's do, but they come out of the run pretty cool.
This 6S setup is making over 2100 watts!
E Revo
MMM ESC
Medusa 36-70-2000kv gearing 14/52
Apogee 6S 3800mah
They came out of this 20 minute run just barely warm and resting at 3.7 volts per cell.