Monsters as Player Characters
James Jacobs (Editor-in-Chief, Pathfinder),
http://paizo.com/paizo/messageboard...rules/archives/drowNobleAsACharacter&page=1#9
It's important to remember that CR adjustments are NOT the same as 3.5's old Level Adjustments. A creature's CR is a measure of its power in a battle against player characters, and takes in to account the fact that the monster won't be "on stage" for more than several rounds; it's not going to be influencing every single role in a game (which is what the PC race modifiers do).
And the "monsters as characters" entries in the Bestiary aren't there to give permission to players to use them as PCs. They're there because those creatures don't have racial hit dice, and thus are custom built each time by adding character levels to them. We probably should have titled these sections "Monsters as Non-Player Characters" since that's mostly the intent.
Of course, if a GM is cool with letting players play monsters, the "monsters as characters" entries help a lot in getting those particular monstrous PCs off the ground. Chapter 12 in the Core rulebook and the appendix of the Bestiary have guidelines for how to handle playing monstrous player characters.