Well, I think they hit it on the head with their comments about why he could be the best: even if everything goes wrong with Wallace (he deteriorates more, he whines about minutes, he gets a ton of Ts), he's still going to be an upgrade over Mikki Moore. And given the fact that I think that last year's team could've won it all with Mikki Moore (had KG been healthy), it's still an upgrade even if everything goes wrong.
And I don't think the worst case happens. I think the best case is that he's rejuvenated and makes it so that when Perk or KG go to the bench, the C's still have two elite big men on the floor. I think that even if he does slip some, he can still be what Rodney Rogers was to us in 2001 and at least help spread the floor for Pierce and Rondo to penetrate.