Please put problems at on the front page and make the subject tabs on the left filter problems. I am sure most people want to solve problems and not practice. Practice is a useful feature but I do not think it should cover up the problems.
As for friends. I would like to have to option of putting my friends list on the front page. Community is not a descriptive name for a place with problems and not to mention, the largest area of brilliant.
So when I log onto brilliant I want to see new/popular problems. Filter tabs on the left. Friends list under that and I can, if I want to, look at practice problems, wikis etc.