It would be awesome if you added "rooms" like in binaryse*** . com. It's the most useful feature I have used. It's a way for you alone or with a friend to pick some problems and concentrate in a timed session with a chat to solve them. After the session you can see each others code and discuss. It's simply awesome!
It changed our studying habits, interview prep can be fun and a good learning experience as well doesn't have to be a constant struggle.