Well, two years ago, the only reason the Cavs series went 7 was 'cause one, we stunk on the road and two, Ray missed all series long.
This time around, however, the road vs home isn't as significant and I believe Ray Ray will be dropping 30, night after night, against the Cavs. And I don't think the Cavs will be able to make the adjustments, because it would open up too many other options for the Celtics to score big.
The problem here is Jamison and if the Celts don't find a way of dealing with him, it can be over in 6. Otherwise, the Cavs aren't a scary playoff team.