BD is spot on. It's explanation and detail, no fundamental changes in plot or mood. Personally, I'm satisfied, but I was never seriously bent out of shape about the original ending.
It does show further importance of your decisions in ME3 itself (EMS, genophage, chosen ending, geth vs quarians, etc...), and gives some added resolution as to your friends' fates.
I think the one minor (but substantial from a closure standpoint) plot change from the original is the possible extraction of your injured crew during the rush. This is something I appreciated because originally the scenarios where one of those crew emerged from the crashed Normandy seemed more like a bug than implication of their actual survival.