Mostly, the review is a long rambling meditation on Halkin’s opinions and assessments of the structure of liturgy, while barely touching on this edition of the sidur. He can’t even bring himself to mention the typeface and only briefly mentions the brilliant design of the sidur.
And he has this to say about Musaf:
There is a logic in the absence of the musaf in Mishkan T’filah. We are beyond all that now, so why mention it?
There is a logic in the emended musaf of Siddur Sim Shalom, too. Our forefathers did what they did and we are not ashamed of it, but it would be absurd to want to do it ourselves. Let us therefore mention it—in the past tense.
There is only tradition in the musaf of the Koren Siddur. All but the more hallucinatory Orthodox Jews know that the Temple will not be rebuilt in historical time and that animals will not again be slaughtered in it. And the great majority of them, if honest, would admit to being thankful that this is so.
I’ve said this before, but I’ll say it again because it’s an important topic to me in liturgy: The history of sacrifice is important. As much as I’m not a big fan of Sim Shalom, I take their approach over the other two here.
The issue with MT’s approach is that it ignores the historical background, the justification for prayer. Prayer replaces sacrifice, with the Amidah at its core. Therefore, for every time that sacrifice would have occurred when the Temple stood, there ought to be an Amidah. There was an additional sacrifice on Shabbat. Likewise, there must be an additional Amidah on Shabbat. It lends to the coherence of the system, which is important.
Why is it important? Because coherence is better than incoherence.