To start things off; as I have mentioned, I am a die hard mecha anime fan. Anything with robots will catch my interest. I have been reluctant lately to pick up any new mecha based animes, mostly because I hold them to a much higher standard. I can say hands down that Gundam is my favorite series, and I tend to compare a lot of mecha shows to it. I have always been curious to watch Mazinger and Getter Robo but haven't really had much opportunity to as they are much more difficult to acquire relative to some of the more mainstream North American anime releases. I am glad I was able to finally get my hands on a few of the Getter Robo and Mazinger series because this one most certainly did not disappoint. Although I ended up picking the last in the Getter Robo series as my first view, I did not feel that there was back story missing. Getter Robo Armageddon was very easy to follow for the most part, without insulting the intelligence of the viewer. All of the pertinent points to understand the story were present. The entire storyline was based on the idea of evolution based on Getter Rays. What was really interesting (even if it wasn't intended) was the fact that besides the story being about evolution, the entire cast evolves not only through the courses of the 13 episodes, but even based on the backstory that is presented through the show.
The one thing I hated about this show is that it has made me want to watch more! Normally this would be a good thing, right? Except for one small problem, the shows are very had to find. I love the fact that this particular show was able to take much of the animation style and keep it true to the 70s and 80s character design without making it plain cheesy. Combining the modern style of animation to the 70s over expressive character expressions made this a masterpiece. I have had a chance to watch some of the original Getter Robo episodes since watching this (not many though), and it has much of that friendly style animation where even the badass characters don't look all too fierce. They really were able to stay truer to the manga character style in this one.
Even if you aren't much into mecha based anime, I would still recommend taking a look at this series, even if it for a few episodes. There is so much happening without being overloaded in terms of content, that it should be able to cater to a number of genre tastes.