they claim to be the most energy delivering cell per kg.
http://www.a123systems.com/html/tech/power.html
3000 watts peak to be precise..
but, if you look to the flightpowers, their 6600 22.2V pack weights about a kg (1013gramms) and is able to deliver 3700 watts.. (fligtpower cells are 3.175 V @ 30C discharge.)
This is about power per weight, not about durability.