Interesting concept. One think that popped to my mind immediately is that you need to avoid accidentally creating filter bubbles, i.e. locking everyone in their own personalized stream that shows only what they like and already agree with. It's dangerous for the mind.
Another thing is that a lot of value people like me derive from hanging out here are the random things you get to discover here - things that one wouldn't ever think about before and thus never upvote something similar. So it would be good to leave some place to splice in some random submissions that are not related to one's personal preferences.
Re filter bubbling, the scheme as envisaged actually broadens it. It shows some random unrated stories at the very top of the list so everyone is constantly exposed to things not in their filter bubble deliberately.
You can show some random unrated stories at the very top of the list, and then stories sorted by collaborative filtering.
In my prototyping it worked super-well.