Let me just preface this by saying that I have also watched the DVD Specials, but I'm not sure if they warrant a separate review for now...so I'm including bits and pieces in here.
Forewarned is forearmed. Baccano! came highly recommended, but plastered with a warning from virtually everyone who'd seen it - highly confusing initially, with events and characters starting to slot into place progressively throughout the series. Geared with this knowledge, I kept my wits about me and tracked an increasingly intriguing and engaging plotline all the way to a stark and fitting conclusion.
Baccano! details several different strands of a complex timeline, spanning a grand total of 290 years at its peak, with most of the action taking place in a three year blast of chaos. At first, these strands seem disconnected and random, but gradually they knit together as the various characters interact and push the story along. With plenty of action, gore and lots of other things to entertain the senses, the anime drags you along with the Flying Pussyfoot (a train, not a bizarre fetish), putting you on the inside of several different Mafioso gangs locked in a power struggle.
However, it's not just a period piece of 1930's America, with shootouts and speakeasies - there's a significant fantastical element involving an elixir of immortality and the concept of a homunculus (I was instantly reminded of FMA, despite the difference in setting...I'm a sad case), which ties in extremely well with the old-fashioned mobster authenticity. It's a minor miracle that this is the case, as it could've gone so disastrously wrong. I can't go on about the story too much as I'll spoil, but it's action-packed, very driven and despite initial bouts of confusion where memory retention is definitely needed, it's worth pressing on to see how things unfold. It doesn't get full marks due to a slight lull in a few middle episodes, and I think that the 1932 arc should've featured a little more than it did.
This is by no means a bad score - however, it's rescued by the sheer attention to detail in regards to the setting. This show practically breathes the classic prohibition-era gangster flick, a historical backdrop that I'm familiar with, and could therefore nitpick to death - except, I couldn't. The colour palette is stellar, with muted tones and washed out swathes of landscape dominating a world of hats and suits, and the locations look massively authentic. I can't praise the research that's clearly been put into the series enough.
My rhapsodising aside, the action scenes are fluid enough, whilst character designs are suitably functional and manage to avoid the glaring trap of everyone in a suit looking the same. There are some nice stylistic touches scattered here and there, with the Rail Tracer's initial appearances standing out. I will, however, dock marks due to overdone blood effects (emphasised particularly by Ladd and his crew), and the anything-but-seamless integration of CG into the hallway scenes within the Flying Pussyfoot.
Relatively speaking, this was the section that impressed me the most. Most of the characters were certainly sufficiently VA'd, with nobody standing out as being particularly poor - I thought that Luck's VA did a good job of portraying a young character as trying to act more ruthless than he actually is, in particular. However, when it comes to seiyyu, I'm admittedly a total newbie who knows nothing about the major players in the industry, so take the judgement with a pinch of salt.
On the other hand, one thing that I know a lot about is music - not much can touch on my personal tastes that isn't firmly rooted in the slice-of-life genre, but the ambient jazz areas of the soundtrack were utterly outstanding. For anything not involving an action scene, the mood was perfectly judged and set, with the sparse piano sometimes fading away and allowing the background noise to gently wash across the bow - brilliant. I find that this works especially well with headphones, which drag you into an immersive world even further. And the action was accompanied by some tense music that got me leaning forward. No complaints whatsoever, the audio work in Baccano! is excellent.
Also, the OP deserves it's own mini-section here, as it's simply amazing. The entire opening was brilliant, but the opening song was phenomenal, an uplifting, cascading jazz piece that was glued to the subject matter and massively catchy to boot. Objectively, it's possibly the best opening song that I've seen.
Difficult section to rate - this was originally lower, but given the sheer number of main characters involved in the series, and the fact that very few of them flopped, I can only praise the characterisation.
Seeing as there's about ninety-zillion different characters crammed into a mere thirteen episode run, it's difficult to speak about all of them. You have some typical hero-types (Firo, Jacuzzi) who are admittedly a lot deeper than your standard shounen half-pint, mixed in with a bunch of other gangsters who vary wildly in terms of justice and depravity. The main antagonist is suitably evil without seeming like a card-carrying villain, whilst the vast array of loose cannons in the series is notable - in an anime where a lot of people get killed, it's a miracle that more weren't killed.
They obviously did a good job in my case with stirring emotion, as I utterly despised at least three characters (especially Ladd, good lord), loved a few more, and generally actually gave a damn about what happened to most of them. Watching some of them change according to circumstance was a joy to watch, with Czeslaw's progression being the one that touched me the most. Mark my words - you will get attached to these characters, and it becomes difficult to remember that most of them would kill at the drop of a hat, quite literally! My only real criticism is Lua, who (as noted in the official review) seemed redundant, only there to enhance Ladd's psychotic nature. As though we needed reminding.
This should probably be higher. But Baccano! is unfortunately the first show to suffer due to the fact that almost everything I've watched to this point has been excellent. When your last five watched anime includes Black Lagoon, Kino's Journey, Death Note and 5cm per Second, it's going to take something mighty special to rise above. Baccano! actually does very well in this regard, acting as a fantastically engaging story with fun characters and a healthy mix of action, suspense and reflection. If you can get past the admittedly bamboozling first few episodes, there's a rich vein of plot just waiting to be tapped, and the main well will keep you transfixed until the very end.