Do not discount Varejao and Waiters defensively, especially Waiters. I think playing next to James will do wonders for Waiters on both ends of the floor. If they can land Marion, they will add another credible defender as well. Center could be a real problem for them as Varejao is always hurt and Haywood just isn't very good, but I wouldn't be surprised at all to see plenty of lineups with James at the 4 and Love at the 5 and frankly against most teams that won't be a problem at all.
Chicago, even with a healthy Rose, will not beat Cleveland. They just have no one to defend James. He will have a triple double field day all day long. Not to mention, even Gibson will struggle to hang with Love. On the other end of the floor I fully expect James to totally shut down Rose, leaving them in a bit of trouble offensively.
Frankly I think Miami might pose more of a challenge as I really expect Bosh to go off. That said the team to watch in the east is Washington as they are the only team that could pose a real problem for Cleveland in the East if everything comes together for them and Pierce can stay relatively fresh for the playoffs. They have the players 1-3 to pose difficulties for the Cavs on both ends of the floor and their big athletic big guys should also do reasonable well on both ends of the floor, especially Gortat down low. That is the only match-up in the East that I would be interested in watching as that is the only team I see with a good chance at beating Cleveland.