(It seems silly of me to try and summarize a run that hasn't yet concluded. But my recent renewal of appreciation for Whedon's Astonishing X-Men - coupled with the increasingly annoyed and/or dismissive responses from a large number of folks in X-Men fandom - prompted me to produce a version of the follow comments on the X-Universe Message Board a couple weeks ago. Exchanges with Jason Powell allowed me to refine and add nuance to those arguments, so I'll try to capture some of that, too.)
First things first: If nothing else, Joss Whedon is responding to Morrison's persuasive, if ultimately nihilistic, appraisal of the X-Men canon with an appraisal of his own. Morrison, of course, set out to rejuvenate the X-Men, make them sexy and overtly political - to approach the other without returning to the norm. (Indeed, I recall hearing Morrison theorize his New X-Men as a dialectical process, where JLA was thesis and the Invisibles were antithesis.) When he failed - and it is unclear whether failure was always already immanent - Morrison resorted simply to a vicious mockery of those same X-Men tropes that he had claimed to have abandoned.
The major difference, then, between Whedon and Morrison is that the latter saw the tropes and canonical stories of the X-Men as a restriction - Morrison says that every writer must do the obligatory Phoenix, Magneto, Sentinel, etc. stories - while Whedon seems to regard them more narratologically as guidelines that are fundamental to the telling of an X-Men story. Which is not to say that Whedon isn't ambivalent about the way that those tropes and narratives are deployed, and I think this is made clear in the very first issue:
1. Kitty sees apparitions from some of Claremont's best-loved stories, so we know the past isn't just in play but will be actively haunting this run. And indeed: Colossus returns from the dead, as do the Sentinel that killed the Genoshans, Cassandra Nova, and the White Queen. Though you can argue that certain exercises are less successful than others, it's an excavation of their history - in peeling back the layers, Whedon's trying to get at an understanding of who they are and the compromises that each of his cast has made along the way. (And, in turn, how they have been compromised by those decisions.)
2. The costume/no-costume discussion establishes that this isn't simply a reversion to an old status quo - Cyclops says that they have to look like superheroes, not that they are superheroes. Mutant politics and ethics take something of a backseat, but we'd be mistaken if we thought they were absent and they'll come roaring to the fore soon enough. In this point, I'm not even talking about the Cure or the irony in imprisoning a mutant computer program. The most poignant political moment is when the team, in costume, fights the Mole Man's monster but fails to be convincing in their act. They don't make the news and they don't make things better for mutants; dressing - performing - as superheroes didn't hide the fact that they were still mutants. (And, in fact, I think that this realization allows for Cyclops subsequent growth.) This is certainly a critique of writers who portray the X-Men as Just Another Superteam, and perhaps even critical of Morrison for trying to situate the X-Men as post-human. Cyclops' ambivalent relationship to mutanity and humanity allows us to recognize that mutants cannot extricate themselves from their humanness and find an 'outside' that places them exterior to humanity as post-humans. But likewise, having been marked as mutant they cannot ever be entirely 'inside' humanity, either.
Where Morrison left us with a dead-end - a critique with no obvious direction forward - Whedon seems to be trying to resolve what the X-Men can be if they cannot be like superheroes. The alternative, it seems, is to shift genres entirely: Whedon's latest arc (which heavily alludes to Dune) seems to take heavy inspiration from the early- and mid-80s X-Men stories that often found the team in space and otherwise battling science-fiction tropes, the sorts of stories and characters that have receded from interest in the past decade or two like the Brood (Aliens), Nimrod (Terminator), and the Reavers (Mad Max). To steal a line that I heard elsewhere, it seems Whedon is saying that 'everything you forgot was pretty cool'.
My least developed thought is on the structural aspects of the four arcs, each of which seems to mirror the various parts of the Phoenix Saga more or less closely. What I wonder is if it's fair to suggest that Whedon is elevating this story to a sort of 'master narrative', the "totalizing cultural narrative schema which orders and explains knowledge and experience" within the X-Men mythos, the control mechanism though which multiplicity is engaged and difference is recognized, registered, and regulated. Certainly, it seems fair to argue that the Phoenix Saga - both its narrative form and tropes of corruption, forgiveness, rebirth - has established the parameters that allow us to makes sense of difference and what it can be "about" within the context of the X-Men.
It might be silly and/or hyperbolic of me to liken the canon of the X-Men to a phallic economy, but I'll go there and claim that the same caveats apply: that Morrison failed to successfully possess and redirect the X-Men precisely because mastery of a 'master narrative' is always delusional. And, sure enough, in the end Morrison seems consumed by an sort of hysterical anxiety - he is able to say what his X-Men are not, but what they are remains ill-defined or even only negatively-defined, demanding recognition from the canon that it has made great lengths to otherize.