I don't usually write reviews, but I noticed that the two reviews for this were bad. I'm not sure why. It told a Decepticon centered story well without, as it might have, rendering the Autobots unlikable or uninteresting to keep the reader's focus on/sympathy with the Decepticons. In making both factions' stories interesting and engaging rather than making the Autobots annoying, irrelevant, or worst of all villainous themselves, it improved on what for me was the major weakness of Megatron: Origin (which I also really liked.) Before I saw those two bad reviews, I would've thought that anyone who, like me, likes the Decepticons and wants to read about more than the 'Cons getting their afts kicked over and over, would like this. As in Megatron: Origin, we see the motivations and desires of various characters in more -- and more convincing -- detail than just "oh, he's conniving/sly/mean/clever/brutish/etc. because he's a bad guy."
I also felt that it did a good job of handling the problem with pacing that the first volume had. Volume 1, as one of the reviewers mentioned, was quite slow, spending a lot of time depicting the destruction and mayhem wreaked by the 'Cons, but very little time on plot. That's fun for Decepticon fans who've been waiting to see them get their chance to trash the place in true Decepticon style (yes, I'm grinning as I type this), but it does get repetitive quickly. This volume picks up the pace considerably.
I think what may be bothering some of the other reviewers is that this story takes place after some other IDW comics. This means that if you read All Hail Megatron by itself, some of the plot twists lose their force because you don't know what happened before. I haven't read those particular comics, so I did feel slightly let down by plot twists that were introduced in a previous series. However, I still thought they were reasonably well done and found myself caring about the characters anyway. Some people might not like AHM because of this (Megatron: Origin does a better job of working standalone), but I don't think it's a dealbreaker.
As another reviewer mentioned, another strike against it is that the art style switches drastically in the middle, from a gritty, detailed style to a cartoonish one. I'm not a fan of the cartoony style, and would have loved to see those scenes done by the other artist instead. Still, the story is the driving force for me, and the story behind those panels worked for me.
I'd recommend this to other fans of the 'Cons especially, but I actually think there's a lot here for anyone to enjoy. As I said before, the Autobots are well-done as well, and suitably impressive when they inevitably show up to save the day (*grumble*)...