I think Krstic is being overrated mostly because few people were confident about him contributing. He was considered a throw-in, so now the pendulum goes the other way. Things will level very soon.
I keep thinking Danny and Doc are 100% sure about the O'Neals health. If not, the free agency signings are not solving the main shortcoming of the Celtics, post defense. Krstic can't be that presence, but neither Murphy, and against the Laker trees, Baby won't do it better (although he's been really good against Howard or Tim Duncan). I had hopes of a little more Sheed, because if Shaq and his brother Jermaine can't play, the Celtics have no real inside force. And with all his flaws, Sheed did it better than anybody (including Perk) in last year's playoffs.
So we don't have to expect Krstic to give the team the post defense Perk can give when healthy, it'd be unfair for Nenad. We must expect the O'Neals healthy and ready for the playoffs, or else the Celtics will have to work some magic to get past the Magic and the Bulls/Heat.