I would add in here that if the off-hand weapon is light, the penalties reduce to -4/-2.
If both weapons are light, the penalties are -3/-1. [Light weapons in my game typically don't do more than a d6 dmg. So if it is listed as d6+1 or as d8, or d10, it doesn't count as light. Thus, rapier and dagger would count).
Elsewise, you'll see far too many paired bastard swords, when you were hoping for rapier/dagger fighters.
Just got this off the Troll Lord Games Board... Looks good to me.