I really like this system, I've been running various Lovecraftian games for over a decade now and definitely like this product.
My biggest problem with it isn't really the system's fault, as I run primarily over virtual tabletops (With a strong preference for Foundry) and being a small system it can be difficult to get on big systems. If you're struggling with this problem, I found that running it as Delta Green (The systems overlap a lot in some ways) and adding in custom weapons and items, as well as having a handout/journal entry telling you your skill with the skills not ont Delta Green's sheet gets around this issue well.
My only other real problem is that the pre-written apocalyptic scenarios are short, very short, with plenty of room to fill in your own ideas, but in turn that leads to them being somewhat uninteresting. Particularly, the setting of "The God from the Utmost South" was one I was excited for, dealing with the creature from At The Mountain of Madness (And, I feel, drawing heavy inspiration from other titles such as Beyond the Mountains of Madness and Assault on the Mountains of Madness) which is my favorite Lovecraft story. It has an interesting premise, rather than destroy the world as we know it in fire and death, the God instead enslaves humanity and turns them into an insect-like hive where people communicate telepathically while hunting down those mentally strong enough to resist. Again, interesting, but the section on it lasts only four pages, with no guidelines on how to actually run this scenario because it's short, to the point that the Keeper is going to be inventing the vast majority of content for it. The sample apocalypses are simply seeds, when I was hoping for full fledged settings, which was disappointing. Notably excepted from this is their section on "The Night Lands", which is 50 pages worth of a sourcebook full of ideas for running a full campaign. I would have preferred another one of these, perhaps for Cthulhu or Nyarlathotep rising, but I have zero complaints about this section. Should Cthulhu Reborn publish a book of more settings like this, it would definitely be worth a look.
Now for the good, however. As I said, the section on The Night Lands is awesome and is brimming with ideas for being based off of a setting a hundred years old that predates Lovecraft's mythos. Additionally, Apocthulhu is widely adaptable by design to be usable with monsters, tomes, weapons and other items of interest from other systems such as Delta Green. It mentions it is compatible with items from Open Cthulhu, but I don't think this product is available yet, I hadn't even heard of it and it appears to be in a legal limbo, so make of that what you will. Apocthuhlu doesn't have specific rules for using Call of Cthulhu RPG items and monsters, but it's easy enough to switch it over should you want to, particularly if you're more partial to 6e instead of 7e. Finally, the scavanging system is intuitive and ensures your players are never truly without the gear that they might stumble into really, really needing while intentionally keeping their resources scarce.
All in all, I recommend this for any fan of Lovecraft, particularly fans of the Delta Green RPG or Keepers who don't want their game of Masks of Nyarlathotep or Beyond the Mountains of Madness to end just because their players caused the apocalypse.
[5 of 5 Stars!]