Besides all of the crazy business metrics and unhealthy expansion Mattress Firm is doing, all you have to do is shop one of their stores to see they have some serious problems. There are three stores in my market that have been open less than two years and they have gone through more salespeople than you can count. The last girl when asked what the difference between two mattress was, she just said "that one has more stuff in it".
If you can't make sales, it doesn't matter how many stores you have. And now that they are public and can't hide their figures, I think you will see an even steadier decline in sales, profit, and share price.