I think that anybody who has convinced themselves specifically that Dwight Howard is coming here is going to be in for a big letdown. I don't think he'll sign here.
However, I do think that the Celts are in a lot different situation. The Knicks essentially wasted two seasons, and gave away multiple draft picks, all in the hopes of landing Lebron. The Celts, on the other hand, haven't really sacrificed all that much. I suppose the Perk trade could fall into that category, assuming that Danny did that because he was worried that Perk would walk. However, even if that's the case, the team we put on the floor every night is a contender, so it's different in kind than the Knicks situation.
Again, though, I don't think Howard is coming here. That doesn't mean that cap space won't be useful, though; cap space can be utilized to gain draft picks and to accelerate the rebuilding process, even if we don't sign a big-time free agent.