Well... to clear things up, he doesn't exactly STOP time, if you watched episode 3 carefully, when he uses his geass in the underground water ravine (let's just call it that...)the water is still moving behind Viletta. It's more like he stops the perception of time of the people he uses the Geass on.
There probably is a consequence to his geass, or some limitations, we probably won't learn about it until later on - like Lelouch's. I feel it might have something to do with why he's paranoid about the locket, maybe time stops for him for a certain length of time while everything else moves forward, causing him to lose everything, which may be why he prizes his only possession dearly (locket).
My other theory is he's some crazy android/clone/test tube baby, so that's why he wants some family values!
(no subject)
There probably is a consequence to his geass, or some limitations, we probably won't learn about it until later on - like Lelouch's. I feel it might have something to do with why he's paranoid about the locket, maybe time stops for him for a certain length of time while everything else moves forward, causing him to lose everything, which may be why he prizes his only possession dearly (locket).
My other theory is he's some crazy android/clone/test tube baby, so that's why he wants some family values!
Just my crazy two cents xD;