Essien is better as a CM than DM.
Form is temporary, class is permanent. I am talking about class.
In terms of a player, whose primary position is in DM, I don't think anyone is better than JM. JM is better than Xabi, Banega, Cambiasso and Toulalan IN THE DM ROLE I am talking about that position on the field, not central midfielders. Essien is the best central midfielder in the world. Cambiasso is an awesome CM. Banega has had one awesome season, he needs to do it again next year. MVB is good but nowhere near JM's class. Alou Diarra is not in JM's class either.
JM will improve Inter. He isn't Cambiasso's replacement - he will partner cambiasso.
Again I reiterate I am talking about player's whose primary position is in DM, not CM.
I don't know what you were watching, but apart from Reina JM was easily our best player last season.