I don't really agree with notion that we're built for the regular season. That terms is generally reserved for teams that are perimeter oriented, score lots of points, and lack defense. That pretty much describes the hawks from a few years ago to a tee. But it also describes the warriors to a degree so in some cases, just raw talent wins out (not to mention that they are underrated defensively).
The biggest question the celtics will have to answer is offensive efficiency. We still lack a dominant scorer and generally, need to work too hard for points in the half court. Horford will really help, and so will the improved athleticism of the team (adding horford, brown, green).
And please pump the brakes on this 60 wins prediction. Is it possible? I suppose but it is at the very top end of possibilities. I think the over/under of of 52.5 is about right.