Some info on critical hits:
Every time you attack, the game rolls a 1d20 to determine whether you hit. If it rolls high enough (hit bonus is irrelevant) then you have scored a critical hit. Typically this does double damage. This can ALWAYS happen. There are things you can do to increase the chance of this happening, and there are things you can do to make critical hits do MORE then double damage.
A list of things that affect critical hits:
1. The Critical Strike/Shot skill - each level increases the chance of scoring a critical hit
2. Flurry does NOT increase the chance of critical hit, except that it gives you one more attack, and thus one more chance to roll
3. Power Attack - Increases the DAMAGE of critical hits, not the chance... with PA, critical hits do 3x damage
4. Keen weapon ugrades typically double the chance at a critical hit
5. One of the LS forms (the one with three blasters, shien?) increases the DAMAGE of critical hits to 3x... when combined with power attack, it's 4x!
6. One of the LS forms (the last one, crossed swords) increases the CHANCE of critical hits a lot (+4 I think?)... it ALSO gives you another attack per round... very powerful.
7. The Massive Criticals bonus on some upgrades adds additional damage (i.e. 2-12) to your critical hits.
For a regular, unmodified lightsaber, the chance of critical hit is 19-20 (10%) and the damage is x2. For a double bladed, it's 20 only (5%). Keen doubles these (20%, 10%) and critical strike adds 5%xFeat Level I think... so a Keen Lightsaber with Master Critical strike would have a 35% chance to critical hit I believe. Basically, this means a critical hit almost every round if you are using Master Speed. This is the main reason I prefer regular lightsabers to double-bladed.