I also have not heard back from Michigan about the PhD program. I've already accepted at Wisconsin-Madison (with funding), but it's surprising they haven't let me know what's going on.
I've heard back from 3/5 schools now, which (I hope!) implies that I have a *slightly* competitive application (they were all acceptance+funding, for reference at OSU, Wisconsin-Madison, Indiana). I'm waiting on two others, University of Michigan and Illinois Urbana-Champaign.
When do I contact them? Is it time to be worried? Who else is extremely worried? Ease my worries!