Main stats:
INT (Intelligence) Often checks to your deck/combat-comp skills
REF (Reflexes) Speed, reaction time
POW (Power) often partially determined by your powerplant and how well you can use it
all three stats are arranged in a triangle -- each point is a stat, with the side formed by two adjoining stats being used as the basis of a skill tree
TANK = uses REF and POW -- put simply, this is your "fighting spirit"
HACK = INT and POW -- this involves using power and intelligence to solve puzzles or problems
STEALTH = using INT and REF, shows your 'cunning'
I'll post some more info here when I can.. (Eiji)