IMO, the salary cap generates more concern amongst fans than it should. By far the most important factor in the long-term health of an NFL franchise is how well it drafts every year. If you do that, you'll be fine. If you don't, you're going to suck. A lot of times poor cap management is the result of poor drafting, as teams use free agency to paper over holes in the roster that weren't filled by young, cheap talent. (I'm looking at you, New Orleans.) That's not to say that good cap management, independent of drafting success, doesn't matter. It does, but mostly on the margins. On that note, I think the Hawks have done a good job. In particular, they've been very good about maintaining future cap flexibility. If all the players currently under contract start to suck horribly, they can purge the cap and rebuild fairly quickly. (Compare that to Miami, which has a boatload of money tied up in Suh for years to come.)
IMO, the biggest nut punch from the Percy fiasco was the additional 3rd and 7th round picks that we gave up. The missing 3rd, in particular, still hurts to this day. Remember that we were forced to draft Britt in the 2nd in part because we had no 3rd that year.