Thanks for your feedback.
I think the differentiating factor with other news aggregators is the argument feature. Lots of times an interesting discussion on reddit or hacker news will get lost somewhere at the bottom of the comment page. By breaking it out to an argument thread it can get more exposure, and be available for other users to read who might have otherwise missed it. I often find the comments sections of sites like this to be more interesting than the articles themselves, I'm hoping this makes comments more readable and usable.
Arguments are decided by votes. The argument is active for 7 days or until the participants decide to call a draw or one concedes. At the end of the 7 days, the argument is ended and the user with the most votes is the winner.
A leaderboard or ranking system is definitely in the works. Right now it would just show all users at 0 though. Scores at this point are just the total number of arguments won. I'm still evaluating if that's the best way to go, but I think it will work well enough to start. Something like the Elo rating system (http://en.wikipedia.org/wiki/Elo_rating_system) used for chess ratings might be better, but time will tell.
UI design is definitely not my strong suit, so I tried to keep it as simple as possible. Your suggestion is appreciated, though.
I've been tweaking the copy at the top of the home page for a while to try to explain the site as succinctly as possible to leave more room for topics and arguments. A sidebar might be a better way to make it stand out.
Facebook integration is definitely on my long list of improvements to make. I think the site would really benefit from integration with a Facebook app. You're not the first person to ask for pics / avatars either. I'll have to see how I can fit that into the layout.
Thanks again!