The reason Nintendo didn't want to reveal much is because they're still not finished constructing Project: Revolution. Very smart move in my book. While Microsoft and Sony already have their systems finalized and complete, Nintendo is taking another year to continue improving and optimizing what will be the ultimate gaming system.
Next year's E3 prediction: Project: Revolution being the ultimate gaming system and the next Gameboy having power and graphics equal to PS3.
Oh Sony, if only you hadn't rushed.
Looks like you'll learn your lesson the Dreamcast way...