Busou Renkin is an anime for those who are looking forward to see lots of action, great battles and a great variety of weapons and characters. So if you are a Naruto/Bleach fan you should watch this one, it will be for sure of your liking and probably (in some aspects) may be considered better than the previously named animes.
The story in this anime is pretty much straight forward, those of you who are familiar with Bleach plot will find the storyline very tentative and it will be very likely of your interest, being similar to Bleach's. A boy wakes up from a nighmare, in this nightmare he protected a girl from a monster, but he was murdered in the process. Later on he realizes that he really died and that, what keeps him alive, is a alchemic artifact known as "Kakugane". Tokiko-san (the girl who saved him) explains that this artifact materializes it's warrior's battle instict into the form of a weapon, an arm, Arms Alchemy: Busou Renkin. The enemies here are called "Humunculus" (is this similar to Full Metal Alchemist by any chance?) and do have "another type" of alchemy power. This monsters have a strong appetite for humans because of the unconscious desire they have to recover the humanity they've losed. Then there are other more powerful enemies like Human-Humunculus (Humunculus with Busou Renkin powers), Alchemic warriors made into something similar to humunculus, you get the point. Similar indeed to Bleach's concept of Vizards, Hollows and Arrancars.
Also the story has a very common sequence, used in most action-shounen animes: you first got a treat to eliminate, you eliminate the enemies in episode one then another more powerful enemy comes in episode 2 and another and then another, the usual. But this sequence asures that the anime has a very wide range of characters which makes the story more interesting and worthwhile. It got it's twists, almost all being around the main character (Kazuki). This twists are what really will make you keep watching the anime to the end, because you will feel very attached to Kazuki, but not to any other character really.
The artistic design is in a very high level. The locations look very good, even when thay get destroyed, and believe me, this happens a lot. But on the other hand the character's design is a bit... gay. Characters like Papillon and Moonface really look like taken out from fairytales. If you have watched animes like Speed Grapher you will find the appereance of the characters (enemies specifically) very similar and probably like it, if not and you are planning on watching this then get used to it, but don't worry you will learn that this characters really are scary (excluding Poke-Moonface Mooooooooon! Definitely one of the most stupid character's I've seen.)
Continuing on let's talk about the sound. I have to say that this anime's soundtrack rocks. The opening is superb and almost all sountracks are just the perfect match for the Busou Renkin concept. Without the appropiate music the battles really would have been boring but, actually, the strength of this anime lies here: the battle soundtracks are stunning, they do give the battles more drama and spice and definitely makes them feel really sort of heroic, far from being boring. The ambience themes are also perfectly inputted and give the peaceful / critical feeling depending the situation.
Characters are as various as episodes are in the anime. We've got personalities from idiotic and childish to sorrowful and really evil. Most of the characaters, as mentioned before, have a staraflarious look that doesn't escape from being stupid. But even so the personalities are not reflected by the looks. Take Papillon for instance: he may look like a butterfly, and some times act really gay but when he get's serious he really does look scary as hell. Every character has a different power (at least those who posses a Kakuganes). These powers are really original and different, are mainly represented as weapons. But actually each weapon have a different property, this properties go from high speed regeneration to gravity control, so really a wide difference between weapons.
Regarding the personalities itself I have to say it's impossible not to take notice Kazuki's stubborn and "I wat to save everyone" behavior. At some times the way he acts is really annoying but you will get used to it and, at the end, really love this character. Also these guy get's trashed really bad and, supposedly, killed many times (I counted 4). But somehow he manages to stand up and win the fights, so we've got a hero that always wins and never gives up, even if he is supposed to be dead. A pretty often used model of character in modern Shounen animes to create sympathy around the main lead. The character development, again, only centres around Kazuki. He goes from having no powers to become the most powerful warrior in the Alchemic Society, and that progress does take time but still it gives a good amount of anxiety to go on watching it. Also note he always learns new techniques and, at some point, he unleases his real powers.
This is a pretty good example for an anime that is good, not perfect, has factors similar to other animes, and can still manage to deliver great fun and satisfaction. I really enjoyed watching Busou Renkin. It ended good and there was not need for more content after it's conclusion. I recommend it to anyone, it doesn't matter if you don't watch this kind of animes, because really it's just the same formula that other animes, like Bleach, use. But Bleach is popular isn't it? So that means the formula works, it worked for me at least.