Just read issues #5 and #6, and man, it is not good, despite some rather interesting stuff in #1-4 (I really liked Jean Grey’s psychic war with Karnak).
The main problem, to me, is that the writers never figured out how to finesse the basic premise and service the characters at the same time. The big moment in IvX #6 is Medusa deciding to destroy the last Terrigen Mists because the alternative is the death of all mutants and only a monster would allow that to happen on their watch.
Which is a great moment if you want to make Medusa look super-heroic…except that “Terrigen Mists will kill all mutants” was the basic setup for BOTH Inhumans vs. X-Men and Death of X. Medusa has known all of this for ten issues/more than eight months, and in all that period was staunchly on the side of “preserve Inhuman culture” to the point of war. Not only is there no catalyst for Medusa to change her mind, there’s not even a moment where she really wrestles with 1. Black Bolt causing this problem in the first place, 2. the fact that she’s killed multiple people to back his play (and no, her “I hated doing that” doesn’t count), and 3. she herself was saying mutant-genocide-is-inevitable, oh-well, we-are-the-future-and-mutants-are-the-past for a while, so it’s not like she hasn’t thought through any of the broader implications of her actions.
And given that Issue #4 set up the idea of the younger Inhumans revolting against the older ones and then #5 and #6 squander it by having them just deliver a MacGuffin, you can almost see what a real confrontation with them would have looked like, forcing her to realize that you can’t fight for the idea of Inhumanity if real Inhumanity is screaming “not in our name.” As a result, IvX #6 reads as a super-clumsy author saving throw meant to A. keep the Inhumans looking enough like “good guys” to be viable properties, and B. get Medusa to her pre-determined end point of hanging out with Black Bolt in his new nightclub, without actually putting in the work for the characters to earn their endings. (Complete with a chunk of Emma’s face on the bar…which is creepy as hell.)

Likewise, the flip-side of this moment is Emma Frost going evil. Now we’ve seen that setup from the end of Death of X, but man does it just go from 0 to infinity-stupid in a heartbeat. One moment Emma Frost is an ideological extremist trying to burn Cyclops-the-Martyr into the collective mutant psyche, the next she’s mind-controlling everyone and building anti-Inhuman Sentinels and getting a face scar (BECAUSE SHE’S FLAWED, GET IT) and putting on a Magneto/Cyclops helmet and spike costume
– and at this point my eyeballs were rolling up into the back of my head.
I’m fine with Emma Frost as a villain but “women can’t get over their exes” is not an interesting motive for a villain, especially when the specter of Claremont’s Emma Frost, a plain-dealing villain who was manipulative and ambitious and ruthless and above all independent and self-directed in her choices, is hovering over the new status quo. That Emma Frost would despise what we have now.

There’s a lot of stupid stuff along the way – characters changing sides and motivations on a dime, fights where characters are winning or losing seemingly based on coin flips, lots of muddled crowd scenes, dei ex machina out the ying-yang – but that’s just standard Bad Event Writing/Arting.
So in conclusion:
Now that we have all of IvX and can look back over the whole, it’s even more glaring that this whole thing was Soule and Lemire doing Death of X again and trying to get it right this time. Unfortunately, they couldn’t stick the landing last time, and they didn’t stick it this time – which means the better part of the X-line for the last 2-3 years has to be written off as an artistic failure.