I have personally finished all of D Gray Man and this is my review for it.
Story :
The story starts out really well, showcasing Akuma and Allen and an organisation to defend the world from the evil of the earl. Nice. However, the story get's really repetitive towards the end and at a lot of points you will force yourself to watch through it.
Art - 8 :
Art is really nice, great world and animation.
Sound - 9 :
Again, nice sounds and effects.
Character - 5 :
The main character, Allen is not a typical character at all. Allen is not the kind of character that would go for the greater good and isn't very emotionally strong, crying at every emotional turmoil, don't get me wrong it's good to cry once in a while, but it's taken to a whole new level.
Along the way, it seems the mangaka forgot who the main character is and instead decided to focus on another character, Lenalee giving her way too much attention and importance. Lenalee herself is another typical too emotional character that seems to cry at every other point, disturbing others.
There are quite a lot of unique characters in the mix that you love, but the above characters have the most impact.
Enjoyment - 7 :
The anime itself end abruptly in the middle of a supposed-to-be long arc confusing you and leaving a lot of unanswered questions, the story has plot holes scattered around. The story also frustrates you at more than one point.
Overall - 6
If you want an anime where you have a typical crying girl and a hero who so conveniently shows up at the last second just to look badass, this is your anime.