I think there are two reasons this is a worse matchup (Lebron is involved and they have rebounded well against the Cs, especially on the offensive glass) but more reasons why this is a better matchup for us than Atlanta was.
1. No underestimation. Game 3 in Atlanta we showed up and played but didn't honestly think they could beat us until it was too late. Game 4, we thought Game 3 was a fluke, made no adjustments then thought it was over when we had a 10 point lead after 3 quarters, so we ended up losing even though Atlanta didn't even play that well. Game 6, again, we thought it was over after the Game 5 drubbing. We consistently underestimated the Hawks, but that won't happen against the Cavs simply because of the amount of respect everybody has for Lebron.
2. Lack of athleticism. The length of Atlanta's 2-4 players clearly bothered us. Smith, Childress and Williams were consistently able to crash the boards from the perimeter to disrupt our defensive rebounding. While Cleveland is a better rebounding team than Atlanta was, they are much more traditional and don't pose the same problems as far as guys crashing the boards from the perimeter and disrupting the defense.
3. Wake up call. After the trouble we had on the glass with Atlanta, I think we'll be focused on that aspect of the game against Cleveland. The Cavs hit the offensive glass very effectively against us, getting 10+ offensive boards in 3 of 4 games. However, I think we're more ready for it now.
4. Bodies match up. Starts with KG. He'll be matched up against lesser offensive players like Joe Smith, Anderson Varejao and Ben Wallace, so he will be more available for help defense and rebounding. The game he didn't play was the one where Cleveland really killed us on the glass. Cleveland had 17 offensive boards to our 22 defensive boards. Keep in mind, we only lost that game by a point in Cleveland.
Beyond KG, we're not going to be stuck playing a 6'6" subpar defender straight up on a 6'7" younger more athletic All Star 2 guard. Instead, Allen will have Wally, Gibson or Delonte. Rondo will have West or Gibson. Both of those matchups will be much better than Joe Johnson or Mike Bibby. Pierce or Posey will have Lebron which is a tougher matchup obviously but those two are much more capable against a guy like Lebron than Allen was against Joe Johnson.
It will come down to the ability of Perkins and Brown to contain Z without fouling him too much, as we don't have the depth at center and Z is actually an outstanding free throw shooter. He's too big for Davis and Powe, but he suits Perk and Brown a bit more. He's older and slower than Horford, and since KG will be more available for help defense on penetration (which can only really come from one source), they can stay at home with Z, something they couldn't do when they had to react to Childress, Smith and Williams crashing in for Atlanta.
5. Pace. Cleveland plays a slow pace, just like we do. The fact is, Atlanta can't play a halfcourt pace at all, which is why we destroyed them at home when we dictated tempo. But they're an effective transition team because they're so athletic, so when they got the tempo going their way in Atlanta, we couldn't keep up.
Even in Cleveland, the Cavs won't be pushing for a transition-type game, they'll be going for a half court set when they want to set the tempo. In fact, we might be the team more aggressively trying to raise the game's pace because Cleveland is too slow to play that type of game (with one obvious exception). Overall, the pace won't be a detrimental factor for us like it was against Atlanta.
Still, Cleveland is significantly better in the halfcourt set than Atlanta was, so I don't see any 20-30 point blowouts in this series. I personally see us taking 3 games by 8-12 points, 1 close game and losing 1 close game. My guess is the Celtics take the first three then drop one in Cleveland (Lebron should be good for at least one win per series, even against a superior team) before clinching at the Garden in 5. That is provided we execute our team defense and Perk and Brown can stay at home on Z without having to spend too much energy on help defense. If Z opens up for a big game or two and the Cavs can control the offensive glass, this will be a long series and it's be hard to predict which way it will go.
And I agree with the Cavs guy. I always thought the trade made them better, I just never thought it made them substantially better as the media seemed to say it did. Suddenly, they were right in the thick of it with Boston and Detroit. Honestly, it helped them a bit, but as I thought when the trade happened, it didn't change them much - before the trade they were going as far as Lebron took them, after the trade they're still going as far as Lebron takes them.