I personally think this is probably a good solution for visibility. If the issue is visibility of new submissions, random promotion of them to the front page seems like a valid solution.
Though it might also mean that scores will be more variable for new submissions, and that may have an impact on front-page/2nd-page variability and bounciness, which doesn't seem like it would be friendly to casual users.
Hmm, well the way I was imagining it, every new post will get the same amount of promotion, but it's true that it is random in that you never know who you are going to show it to. Some people might pay attention to the New Posts box, some may not.
Though it might also mean that scores will be more variable for new submissions, and that may have an impact on front-page/2nd-page variability and bounciness, which doesn't seem like it would be friendly to casual users.