If Deng stays healthy, he's got as good a chance of just about any non-superstar player you could add to that Cleveland rotation to turn them into a 50 win team. He's got well above average passing skills for a 3, he's an elite defender, a minutes soaker, he's exactly what the Cavs need.
But as others have said, he's probably too much, too soon.
For Chicago I think it makes a lot of sense. Nobody was willing to pay much for Deng, and by doing it this way, they get under the salary tax in 2013-2014, which of course they would never have tried to do if Rose weren't out for the year, but now that he is, they can dodge a year so they can potentially use a year later and still avoid the repeater Tax.
So they'll save like ~7-8 million from Luol Deng's actual salary (call it 7.5mil), they'll save another $14 million in lux tax payments, they get a 1st round pick, and they get to exceed the cap in 2 of the next 3 years without worrying about the repeater tax.
Pretty important move. Saving $22 million, getting a future first, couple seconds, and getting another year of potential lux tax eligibility.