My favorite Marvel character is Cyclops, my favorite character is Superman. So I'm a bit worried with Bendis getting pretty much total control over Superman.
His Uncanny X-Men and All New X-Men actually started pretty strong to be honesty, he seemed to be picking up from where Gillen left in AvX Consequences, the characters he introduced were mostly cool and the "mutant revolution" was really promising, and actually his books were the only place where Cyclops and his group was allowed to present their point of view and actually defend themselves, while all the other X-Men and Avengers related titles treated them as villains and incapable of arguing on their on defense, so at least that I have to give him.
But somewhere along the way Bendis apparently lost track of what he was doing or the interest on the comics. The characterization went kind of off, the plots went nowhere and them we have The Last Will and Testament of Charles Xavier, that arc was just awful. And to complete, the mutant revolution didn't happen. Now, some of those problems I think wasn't completely his fault, since I find the fact that Uncanny X-Men 600 was hold back during Secret Wars and only came out when it was clearly irrelevant to the MU show a certain editorial hand.
So if Marvel will miss him? I don't think so, the same way I don't think DC would miss Scott Snyder. But I gotta say, that for the disappointments I had with him lately, Bendis Defenders was really good, remind me of his Daredevil run, so I'm more optimistic with him on Superman. Marvel will be fine without him, the writer who seems to be guiding the ship is Aaron and Hickman is coming back.