Which reminds me of the other thing I really like about True20. It defines heroes by what they do, not what they call themselves. It does not have classes, it has roles and the difference, subtle as it is, is very real.
Classes are a collection of abilities to make the character do things according to a certain archetype. If you want a guy that uses swords, magic fire, and chain mail, then he'll have a different class than the guy that uses a crossbow from cover, or the frenzied warrior who rushes into and revels in close combat.
Roles are a character's role in the story. What's the character's primary job in the story? Characters defined by their combat prowess generally use the Warrior role (though they have other abilities; they are heroic in ability if not in personality). Characters defined by their breadth and depth of skill generally use the Expert role (though they have other abilities; they are heroic in ability if not in nature). Characters defined by their manipulation of supernatural forces generally use the Adept role (though they have other abilities; they are heroic in ability if not in character).
And it allows for characters to mix the various types of characters, using multi-role rules and backgrounds (favored feats and favored powers cut back on the need to level-dip).
I've found that 95% of all character concepts, and 98% of actual characters, are easily built using the existing roles. If the Narrator is willing to generate new Core Abilities for specific concepts then those rates change to 96.5% and 99.87%