” 6,000 kg (13,228 lbs) payload up-mass to LEO;
3,000 kg (6,614 lbs) payload down-mass
Payload Volume: 10 m3 (350 ft3) pressurized,
14 m3 (490 ft3) unpressurized “
http://www.spacex.com/dragon.php
I forgot to say that they are probably working up to full payload capacity.
This is only their second trip.