It's funny that you started with the Hawks. I was just atlking with a friend of mine earlier (he's a Cavs fan), and I told him that I think the team that's really going to fly under the radar this year and end up being a major contender will be the Hawks. Will they crack the top five in the East? Probably not. But, you never know.
I say this for one, they took the Champs to 7 games. That has to be a huge confidence boost. And, they have quite an athletic big three of their own in Smith, Horford, and Johnson, as well as an athletic bench. Add in the veteran presence in Mike Bibby and you have a formula for success. I wouldn't be surprised if they gave the Celtics MORE trouble this year.
And your right, they have a lot to prove, BUT, I'll be willing to bet they'll be an eastern conference threat this year.