I think that the Celtics are in big trouble now that Shaq looks like he is destined to not contribute in any effective way, shape or form in the post season. But I still think that the Celtics are slight favorites in the Eastern Conference. They don't have an offensive player anywhere near the caliber of D-Rose, but they do have 4 offensive players (Rondo, Pierce, Garnett, Allen) who are all arguably better than the guy who needs to be our 2nd best offensive weapon (Carlos Boozer). The Celtics' offense is flat out better and more refined than the Bulls. They have better ball movement are are more dynamic.
People talk a lot about the Bulls' defense being the best in the NBA, but it's really hard to say that when you note that the Celtics team also developed under the guidance of Tom Thibodeau. Sure, the Bulls have Ronnie Brewer, Luol Deng, Joakim Noah, C.J. Watson, Taj Gibson, Omer Asik, and Kurt Thomas. But not all of those guys are going to be getting minutes worth speaking about by the time they get to face MIA or BOS (assuming they beat ORL). The Celtics' defense has a weapon in Kevin Garnett that is still a DPOY candidate and the best pick-and-roll defender in the league. He gets in passing lanes about as well as Rondo does, and it a shot-blocker around the rim. The Celtics will surely be hurt by the lack of Kendrick Perkins. But their defense is just as good as the Bulls, if not better.
The Bulls do have a nice advantage on the glass. That can't be overlooked either. Boston is by far the worst offensive rebounding team in the league. And now that Shaq is gone, it is more than fair to say they will have their problems like they did last year. But KG is back in good health and is capable of getting 8-10 rebounds per game. It's no match for the Bulls. But if Boston somehow manages to close the gap in a series, head-to-head with CHI, it may be over for the Bulls' Finals' hopes.
As for the Lakers, this is a team that absolutely dominantes offensively and match-up very well with the Bulls defensively, as well. The margin of differential on the glass won't be so great either.
The Thunder are a team that are very inconsistent. But they have already shown the capability of being able to play some great defense since Perkins has arrived to defend the paint next to Serge Ibaka. That is an absolutely athletic team with great skills. They have Thabo Sefolosha who is better than any perimeter defender the Bulls have. And they have Durant and Westbrook who are both nearly, as dynamic of an offensive player as Derrick Rose is.