Deadman Wonderland is equal parts an over the top mess and equal parts a gritty prison drama, in my opinion. The drama is incredibly overblown, Ganta screams and rants and raves far too often, and it's just dark and depressing on the whole, with eyes being gouged out as punishment after losing a fight, unborn babies being taken away from the rightful father after the mother dies, brainwashing, and heavy doses of grim everyday prison life.
But it's passable entertainment, I suppose. In the same way you can derive enjoyment from Battle Royale (which is where the collars in Deadman Wonderland probably come from) which is a film about kids being dumped on an island with weapons ranging from lethal (a sickle or a crossbow) to fairly useless (a pot lid and a pair of binoculars), and are forced to kill each other for entertainment, Deadman Wonderland does provide its own empathic spectacle. I got quite involved in the setting, for example - Deadman Wonderland itself is the worst prison imaginable, and you do really feel for the poor people in the G Unit, convicted because they won an extremely unlucky lottery when it came to haemokinetic superpowers. So props to the anime writers for that, but I still feel the series was a wee bit rushed and ran around doing cool and gorey stuff for the sake of doing the cool and gorey stuff.
The animation palette is, as you'd expect, quite dismal and dreary. Lots of greys, greens, blues, occasionally stark whites in the prison, with incredibly bright primary colours when we see the Deadman Wonderland theme park, or heck, even Promoter Tamaki's office. It's a nice contrast between the prison itself and the prison's projected image.
The lighting choices also contribute to this effect, but not really in a good way. I consider myself to have a good monitor, and I tend to keep my screen on full brightness level, but the scenes with little or no lighting were incredibly difficult to see. I could see the shapes of the characters moving, but no details other than that. Now, this choice is pretty detrimental, but it does help it somewhat. The animation would look extremely out of place if the prison scenes were brighter in colour, so kudos to Manglobe.
Also, I remember the animation being pretty darn good in the action scenes. The rest of the series wasn't quite so action-packed, so obviously the budget was just par for the course like you'd have in any other anime. It was nothing stellar, but awesome all the same. I could look at a Branch of Sin forming in a carrier's hand all day, like some kind of macabre lava lamp. No, I am not a serial killer.
I'd put the soundtrack in a fairly middling place, because you don't seem to hear much of it. There are two catchy pieces of background music, but I found the whole soundtrack to be rather muted, kicking up to a blare only in the more intense action scenes. The opening theme was this okay-ish emo-esque rock song sung in English that was only really saved by the awesome imagery and use of animation in the intro. And the ending was a very gentle song by Nirgilis, aided greatly again by the animation in the ending credits - a ferris wheel rotating while photographs of the characters' past lives faded in and out. An interesting choice, and a decent way to give backstory to the characters who didn't have any alotted time to get developed.
Speaking of characters, I never felt Shiro belonged there. She may have been there to lighten the tone and to be an important figure in Ganta's life, but otherwise... nope. Some of the characters were a bit underdeveloped and deserved better, and I would have loved to see a bit more of a detailed look into quite why Tamaki is so twisted as to use the prisoners as toys for his own amusement. Ah well, I suppose that's what the manga is for...
In conclusion, I'd have to say that Deadman Wonderland is a very entertaining show if you like bleak prison drama/horror, but it could be offputting for others. The animation is good, if a little dismal with its colour and lighting choice, but unfortunately a patchy story threaded together by weak characters who would have done so much better with more backstory/episodes to develop them (rather than still drawings in the ending credits) really bumps it down a bit for me, so I'm giving it a 5/10 over all.