While the feeling of "this is your destiny, find these items" has been used time and again, D. Gray-man does bring some interesting spins. However, this does not ignore the difficulty of such a broad thesis, so to speak. I think that Hoshino realized rather belatedly that it's difficult to keep the reader interested in a manga that will go on for quite a while. There are 109 or so Innocence; the Order must find them all. I think that Hoshino realized this would take quite a long time, and that it was taking on a Tsubasa Chronicle-feel (and we all know how that went...). It scared me a little, how the plot seemed to be a little similar to Tsubasa's. It is my belief that, after realizing this, she added in, "Oh, wait! If the Earl finds the Heart, we're all dead!"
After that declaration, the story seems to peak at the arc with the Ark (hehe... is that considered punny?). After the Ark, everything had this new feel to it, yet Hoshino let me down by not taking advantage of this new start. Then there were complications and the storyline slowed down, eventually becoming as twisted as Tsubasa Chronicle, of which my gut had warned me. What really disappointed me, as a former (well, I guess it is more accurate to say dormant) Yullen fan, was chapter 176. I remember it clearly because that chapter just killed me oh, so much. It is possible, though, for Hoshino to recover from this literary slump. Only time will tell, I suppose.
A very prominent factor in drawing me into this manga was the cast of characters. Though yes, they seemed to be easily grouped into certain "types" of characters (Kanda, for a while, seemed to be a long-haired Sasuke to me, even though Kanda's my favorite character and I cannot bear 95% of the characters in Naruto, including Sasuke), Hoshino finds little ways to begin to wedge them away from that grouping... and after the Ark, slaps them back in the category, which disappointed me-- very much so. However, there is a chance for redemption.
Throughout the time I read the manga, I enjoyed it very much until it seemed like a down period for Kanda, and after 176, I had no will to read it anymore because I was so shocked by what Hoshino had done to him. I got over it, though, and was shocked again. The plot twists involving Kanda wrenched my heart (but maybe that's because I'm biased).
The artwork in the beginning was very good, but it became even more beautiful as the series progressed. Every panel was like a flower blooming; every battle scene was depicted with clarity-- until after the Ark, when Hoshino began having health problems. I will concede that carpal tunnel does impair an artist's ability, but one of my closest friends has carpal tunnel but continues to produce beautiful work whose quality surpasses that of everything she had every drawn before. But I digress.
Character designs are all very unique; costumes and hairstyles are outlandish yet somewhat realistic at the same time. The only person whose hair is unnatural is Allen, and... well... he's not natural. Also, white is a natural color... just not on a boy of fifteen (is that how old he is?). All of the designs are acceptable in a realistic, modern setting (costumes and clothing aside). It is filled with lots of eye candy (Kanda and Lavi ♥),
Overall, D. Gray-man is a very good manga-- to a point. I would like to think that Hoshino has lost interest and needs to be invigorated with the power that once compelled this author to write such a great beginning. Although I have lost interest, perhaps I will come back.
