"Big Time Machine' isn't quite accurate.
Shaq has played extremely well so far this season, but his play can't really be considered "throw back" peformances. Shaq is doing very little posting up, and when he does he more often than not passes out of the post. The times I have seen Shaq try to post someone up, he has had moderate success at best.
Shaq is contibuting on offense as much as he has because this team understands how to use him better than any of Shaq's most recent teams. It also helps that we have so many good passers on our team, Rondo and KG in particular.
As far as Shaq's defense and rebounding, I don't think much has changed from any of his most recent seasons. Shaq will always get defensive rebounds because of his size. He doesn't even have to try to box out, but still box out. His defense is what it is. He can defend in the post, but anyone penetrating the lane off of a pick-and-roll will just go right around him (have seen this numerous times so far this season).
The biggest differnece for Shaq this year, as opposed to recent seasons, is good coaching by Doc, being surrounded by quality players, and a good team atmosphere that has Shaq very happy and involved. Plus, we know Shaq hates Kobe, and would love nothing more than to destroy him if we both get back to the Finals. This means Shaq is more motivated than in quite a while.