It seems like he's lost his edge. I was reading an article on "the return of Eminem" in some magazine a month ago or so and they were saying how it's been so long between albums, that the world has changed alot in his absence. He's no longer controversial because of how we've had time to get used to his kind of antics by dealing with crazier and more controversial celebs in the mean time. They also go on to mention how the novelty of a white rapper may be gone for many people now that there's a "black president". The world's harder to shock than it was 5 years ago.
I'm not sure about the reasons, but I do agree that he's lost his shock and for me he seems to be trying too hard. He needs to be kind of like "yeah, here's the album. listen to it or not, whatever" instead of trying to tout it like it's the greatest rap album to come out. Most of that's probably pressure from the marketing department but still.
It's kind of like South Park, when it first game out everyone was like "what the heck is this!? this is the most controversial thing ever!" and now look at it, yeah it's still funny (to me anyway) but by no means causes an uproar like it used to.