What it is! (And, what it ain't...)
My unit arrived with the foam detached from the center, but was easily fixed with superglue. Just for kicks and giggles, I assumed that I was a dude who wanted to sound like I was in a pro studio, except in an untreated bedroom. Of course, it made very little difference.
However, in a treated rectangular room, this begins to show more of it's worth. It helps focus the vocals and - take the mud out of the signal. In a proper recording space, it's a good way to reduce reflections to inaudible levels, depending on the type of music being recorded.
Keep in mind, don't put the microphone too close to the foam - you'll end up getting an even muddier and closed off sound that is unusable. Give it at least a foot - in fact, I often use this with a second stand so I can position the mic more easily according to the openness I want.
As usual, there are no magic bullets, and this is not one of them. But a little experimentation can yield some useful results.