Let's start with the clearance arguments - whether the merger would or wouldn't lead to a substantial reduction in competition, an 'SLC'. This was always going to be an uphill ask for the appellants, and so it proved. The court agreed with most of the SLCs the Commission had found.
It's not a great idea to give good advice away for free, but here's some anyway for NZME/Fairfax: don't even think about appealing the clearance judgement. When a judgement says at  that in the online news market "the merged entity would employ over 300 more editorial staff than the three next biggest mainstream media organisations combined" and at  that "The Sunday newspaper reader market is a duopoly so that each firm is the greatest constraint on the other", you haven't a snowball's.
On to the authorisation arguments - whether there were net benefits to the public that compensated for the adverse effects of the SLCs.
The first point traversed was how the net benefit test should work. One argument was that the balancing exercise to determine a net benefit should count benefits in the markets where there were SLCs, detriments in the markets where there were SLCs, and any benefits anywhere else, but not costs anywhere else.
This is manifest nonsense from any economic, commonsensical or public policy point of view: why should some of the detriments be ignored? The trouble was, though, that the Commission, in its 2013 Mergers and Acquisitions Guidelines, went with the lawyerly view that this daft detriment test (DDT) was indeed what the Commerce Act and its jurisprudence required. In its NZME/Fairfax decision, however, the Commission decided to count the detriments elsewhere (particularly the national cost of loss of media plurality). The appellants, wholly understandably, called foul.
I'd thought that the DDT had been definitively and rightly knocked on the head in the various Godfrey Hirst cases (see 'The net benefit test' and 'Common sense - at last'). But whatever lingering zombie existence it still may have had has been well and truly terminated now. Sample quotes from the decision: at 
It is inconsistent with Parliament’s approach to infer, without any clear indication of such an intention, that Parliament intended to discriminate between the scope of benefits to which the Commission could have regard, and then a narrower subset of detrimentsand at 
Proposed mergers will have widely varying levels of impact on New Zealand consumers generally and where those impacts are as broad and as significant as arose here, then it would be inconsistent with the statutory scheme to require the Commission to ignore them. Parliament cannot have intended such an outcomeand at 
The broader approach in the Court of Appeal’s reasoning in Godfrey Hirst 2 suggests the detriments that may be taken into account need not be confined to those arising in the relevant market. Non-quantifiable factors may be decisive, and no logical reason for limiting the type of detriments is suggestedand at 
There should not be an artificially limited assessment of detriments if such limitation would prevent the preferable advancement of the long-term interests of consumers. That cannot have been parliament’s intentionand at 
it would be illogical to exclude consideration of identifiable detriments that affect an overall assessment of the benefits to the public merely because those detriments do not arise in the market in which the merged entity would operate.The DDT is now buried at a crossroads with a silver stake through its heart, and good riddance. Our competition regime is the better for its demise.
The next bunfight - once it was established that the Commission could indeed count detriments elsewhere, even touchy-feely ones ("Non-quantifiable factors may be decisive") - was whether the Commission had been right to put a large adverse value on the potential loss of media plurality. In short, yes it was.
The court didn't much take to attempts to put a number on the plurality loss: at  "Material unquantifiable detriments are simply unquantifiable". And at  it sympathised with merger parties that "it can be frustrating for participants in an authorisation application to be confronted with an outcome that is determined by findings of unquantifiable benefits or detriments".
But at the end of the day someone's got to make the call. It mustn't be a guess: at  "a decision on such matters must strive not to rely on a purely intuitive judgment and is to avoid undisciplined subjectivity". Rather, still at , "An outcome determined by application of unquantifiable factors (detriments and/or benefits) is a matter of qualitative judgement, informed as in this case by expert opinion".
And in this instance, at 
We are satisfied that maintaining media plurality and the quality of the media produced are fundamental values of benefit to the public and of real and national significance.There were also arguments about the Commission's processes. In the end, none of the objections - the Commission only talked to anti-merger people after its conference, it commissioned a hatchet-job rather than an independent expert report - stuck. But if the Commission's got any sense it will take on board, from this judgement, ideas for improvements in how it goes about its business in those two areas.
For economists, there are other interesting points in this judgement. If you haven't mugged up enough on two-sided markets, you'd better, and especially that article cited at  and quoted with approval at  ("We agree with that analysis of the two-sided markets in which the appellants operate"). And there are some aspects of the economics of this case that I wouldn't mind challenging at some point.
Market definition, for one: at  the court said that "The appellants made the superficially attractive submission that it was illogical to find the prospect of an SLC in a market of undefined scope", but I'd dispute that "superficially". How to treat "wealth transfers" to non-New Zealanders in the net benefits test - see  to  - where in my view the law is at best chaotic and probably wrong. Even the basics of how to decide if products are substitutes or complements, for example when as in this case you observe people consistently visiting different online sites ("multi-homing").
But that's enough free analysis for one day.