Wonderfully animated, excellent sound, and great coreography! Everything else? Abysmal.
They couldn't even bother to make Terra's ability coherent. First he somehow survives a giant laser which cuts through rock like paper. His ability requires him to say "precedence self -> laser" or something but he just gets baked alive. Then he reappears in the next scene, literally says "I can survive anything, so long as it's just one thing at a time!" ... Not 5 seconds later his comrade drops a rock on him and he dies. It's just... Sigh.
The series contains almost no plot or character development; it's merely one battle after another mixed in with contradictory terms, lots of talk no jutsu, and so many "gotcha" moments that it becomes routine. The entirety of Accelerator's screentime involves him rambling about being a villain while doing absolutely nothing villainous. Index is seen in the shower and chasing a cat. Some random people get involved in the story only to die immediately. Stuff blows up more often than a Michael Bay movie and I have no idea why I should care.
The coup de grace? A battle... for lunch. No, really. I quit watching. How did it get EVEN WORSE?